Articles de revues : « Tetragonal to monoclinic transformation »

1

Kelly, P. M., et C. J. Wauchope. « The Tetragonal to Monoclinic Martensitic Transformation in Zirconia ». Key Engineering Materials 153-154 (février 1998) : 97–124. http://dx.doi.org/10.4028/www.scientific.net/kem.153-154.97.

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KUDO, Haruhiko, Hiroyuki MIURA et Yu HARIYA. « Tetragonal-monoclinic transformation of cryptomelane at high temperature. » Mineralogical Journal 15, n^o 2 (1990) : 50–63. http://dx.doi.org/10.2465/minerj.15.50.

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Hugo, G. R., et Barry C. Muddle. « The Tetragonal to Monoclinic Transformation in Ceria-Zirconia ». Materials Science Forum 56-58 (janvier 1991) : 357–62. http://dx.doi.org/10.4028/www.scientific.net/msf.56-58.357.

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Simha, N. K. « Crystallography of the Tetragonal → Monoclinic Transformation in Zirconia ». Journal de Physique IV 05, n^o C8 (décembre 1995) : C8–1121—C8–1126. http://dx.doi.org/10.1051/jp4/1995581121.

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5

Sun, Jing, Chuan Zhen Huang et Jun Wang. « Effect of TiN Addition on the Low Temperature Degradation of Ceramic Tool Materials 3Y-TZP ». Key Engineering Materials 315-316 (juillet 2006) : 40–44. http://dx.doi.org/10.4028/www.scientific.net/kem.315-316.40.

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Ceramic tool materials, 3Y-TZP added by TiN particles, were fabricated through hot-pressing techniques. The effects of TiN on their low-temperature degradation at 220# in air were investigated. It is shown that TiN can improve the stability of t-ZrO2 and inhibit the transformation from tetragonal to monoclinic phase, and that the content of TiN affects the stability of tetragonal phase and the propagation of tetragonal-to-monoclinic transformation into the specimen interiors. It is suggested that the grain-boundary phase prevents the nucleation of transformation, and that the high elastic modulus of TiN can prevent the propagation of phase transformation by resisting the volume expansion of transformation. When the content of TiN is 20wt%, the ceramic material shows better low temperature degradation resistance.

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Chu, Peir-Yung, Isabelle Campion et Relva C. Buchanan. « Phase transformation and preferred orientation in carboxylate derived ZrO2 thin films on silicon substates ». Journal of Materials Research 7, n^o 11 (novembre 1992) : 3065–71. http://dx.doi.org/10.1557/jmr.1992.3065.

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Phase transformation and preferred orientation in ZrO2 thin films, deposited on Si(111) and Si(100) substrates, and prepared by heat treatment from carboxylate solution precursors were investigated. The deposited films were amorphous below 450 °C, transforming gradually to the tetragonal and monoclinic phases on heating. The monoclinic phase developed from the tetragonal phase displacively, and exhibited a strong (111) preferred orientation at temperature as low as 550 °C. The degree of preferred orientation and the tetragonal-to-monoclinic phase transformation were controlled by heating rate, soak temperature, and time. Interfacial diffusion into the film from the Si substrate was negligible at 700 °C and became significant only at 900 °C, but for films thicker than 0.5 μm, overall preferred orientation exceeded 90%.

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Nono, Maria do Carmo de Andrade. « Tetragonal-to-Monoclinic Transformation Influence on the Mechanical Properties of CeO₂- ZrO₂ Ceramics ». Materials Science Forum 498-499 (novembre 2005) : 506–11. http://dx.doi.org/10.4028/www.scientific.net/msf.498-499.506.

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CeO2- ZrO2 ceramics are considered a candidate material for applications as structural high performance ceramics. In this work are presented and discussed the tetragonal-to-monoclinic stress-induced transformation influence on the mechanical properties in these ceramics. Sintered ceramics were fabricated from powders mixtures containing ZrO2 and 8 to 14 CeO2 % mol. SEM observations were used to study de ceramic microstructures and X-rays diffraction to identification and determination of tetragonal and monoclinic phases. It was adopted the 4-point bending tests, Vickers surface hardness and fracture toughness technique to the determination of the mechanical parameters. The results showed that the mechanical properties were strongly dependent of the CeO2 content, the microstructure and the fraction of tetragonal-to-monoclinic stress-induced transformation.

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Sato, Hideo, Seiji Ban, Masahiro Nawa, Y. Suehiro et H. Nakanishi. « Effect of Grinding, Sandblasting and Heat Treatment on the Phase Transformation of Zirconia Surface ». Key Engineering Materials 330-332 (février 2007) : 1263–66. http://dx.doi.org/10.4028/www.scientific.net/kem.330-332.1263.

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This study was aimed to investigate the effect of grinding, sandblasting by alumina and SiC, and heat treatment on the phase transformation from tetragonal to monoclinic zirconia on the surface of yttria stabilized tetragonal zirconia (Y-TZP) and zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite). The monoclinic phase content of both materials increased with the grinding and the sandblasting, while it decreased with the heat treatment. The monoclinic content sequentially increased with the sandblasting and decreased with the heat treatment to each specific value. The SiC-sandblasting produced the larger monoclinic content than alumina-sandblasting. Furthermore, the content changes of the nanocomposite were larger than Y-TZP.

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Hannink, R. H. J., G. R. Hugo et Barry C. Muddle. « Reversal of the Tetragonal-Monoclinic Transformation in Ceria-Zirconia ». Materials Science Forum 56-58 (janvier 1991) : 371–76. http://dx.doi.org/10.4028/www.scientific.net/msf.56-58.371.

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Yashima, Masatomo, Taka-aki Kato, Masato Kakihana, Mehmet Ali Gulgun, Yohtaro Matsuo et Masahiro Yoshimura. « Crystallization of hafnia and zirconia during the pyrolysis of acetate gels ». Journal of Materials Research 12, n^o 10 (octobre 1997) : 2575–83. http://dx.doi.org/10.1557/jmr.1997.0342.

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Hafnia and zirconia gels were prepared by drying hafnyl or zirconyl acetate solutions. Hafnia and zirconia gels contain both hydroxyl group and bidentate acetates which are directly bonded to the metal ions. Thermal decomposition and crystallization behavior of the gels were investigated through XRD, FT-IR, and TEM. Hafnium-containing gels crystallized directly into stable monoclinic hafnia around 500–540 °C, while zirconium-containing gels first formed metastable tetragonal zirconia around 450 °C. The dissimilar crystallization behavior of the gels into metastable, tetragonal zirconia or into stable, monoclinic hafnia can be explained through the difference in free-energy changes of the tetragonal-to-monoclinic phase transformation.

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Popoola, Oludele O., et Waltraud M. Kriven. « Microstructure and phase transformation in KNbO3 ». Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 août 1993) : 956–57. http://dx.doi.org/10.1017/s0424820100150617.

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KNbO3 is a perovskite ferroelectric ceramic material with important electro optical and non linear optical properties. It can be used in an optical parametric oscillator, secondary harmonic generator and photo refractive holographic storage devices. Its macroscopic properties depend on a number of inter-related features such as crystal structure, domain structure, defects and impurity content. KNbO3 has four known solid phases with decreasing symmetry with temperature: Cubic Tetragonal Orthorhombic Monoclinic. The paraelectric to ferroelectric transition occurs during the cubic to tetragonal transformation. The dielectric properties of KNbO3 have been extensively studied and related to the various phase transformations. The aim of this investigation is to study the orthorhombic to tetragonal phase transformations using TEM.Thin slices were cut from a flux grown crystal and mechanically polished to a thickness of 100 μm with a 1 μm surface finish using diamond paste and isopropyl alcohol as the lubricant.

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Schofield, M. A., M. Gajdardziska-Josifovska, R. Whig et C. R. Aita. « Electron-Beam-induced transformations in zirconia-alumina nanolaminates : An In situ high-resolution Electron–Microscopy study ». Proceedings, annual meeting, Electron Microscopy Society of America 54 (11 août 1996) : 690–91. http://dx.doi.org/10.1017/s0424820100165914.

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Composite systems containing zirconia have been used extensively as transformation-toughening materials based on a stress induced martensitic transformation of the metastable tetragonal phase of zirconia to the monoclinic phase. Recently it has been shown that tetragonal zirconia can be stabilized in zirconia-alumina nanolaminates grown by reactive sputter deposition, when the zirconia layer is less than 6 nm thick. Cross-section high resolution transmission electron microscopy (HRTEM) of these nanolaminates revealed localized tetragonal-to-monoclinic transformation caused by sample preparation. In this study, quantitative HRTEM is used to analyze the zirconia nanocrystallite transformation in situ, by controlled exposure of the sample to the electron beam of the microscope.The irradiation conditions used in this study to induce the zirconia transformation are summarized in Table 1. The mildest irradiation condition corresponds to normal imaging illumination used in this study to obtain high resolution images. Under these normal illumination conditions, the first condenser lens (CI) is used to form a 0.1 μm sized probe which is over focused on the sample by the second condenser lens (C2).

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Manzoni, Anna, Karine Chastaing, Anne Denquin, Philippe Vermaut et Richard Portier. « Phase Transformation and Shape Memory Effect in Ru-Based High Temperature Shape Memory Alloys ». Solid State Phenomena 172-174 (juin 2011) : 43–48. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.43.

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Among the different systems for high temperature shape memory alloys (SMA’s), equiatomic RuNb and RuTa alloys demonstrate both shape memory effect (SME) and MT temperatures above 800°C. For both systems, it is interesting to find a way to control the transformation temperatures while keeping the shape memory effect. One way to change the transformation temperatures is to change the composition in the binary alloys; another is to add a ternary element like Fe. The eight investigated alloys show two different space groups at room temperature. The monoclinic alloys undergo two successive displacive transformations on cooling, starting from the high temperature β phase field: β (B2) à β’ (tetragonal) à β’’ (monoclinic). The tetragonal alloys exhibit a single transition from cubic to tetragonal. A multiple twinned microstructure can be found in all alloys. Transformation temperatures decrease with lower Ru content and with the addition of Fe. The β’ à β transformation seems to be the main responsible for the SME. Compression tests performed in the martensitic phase give a quantitative result of the shape memory effect. In the binary alloys, the SME decreases with decreasing Ru content, which is in accordance with the evolution of the lattice parameters of martensites. A lower SME in the ternary alloys can also be linked to the lattice parameters and seems to be quite reliable to predict the evolution of the shape memory effect.

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Rodriguez, Mark A., Nelson S. Bell, James J. M. Griego, Cynthia V. Edney et Paul G. Clem. « In-situ monitoring of vanadium dioxide formation using high-temperature XRD ». Powder Diffraction 29, n^o 2 (7 mai 2014) : 97–101. http://dx.doi.org/10.1017/s0885715614000311.

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The monoclinic-to-tetragonal phase transition (~70 °C) in vanadium dioxide (VO2) strongly impacts the infrared properties, which enables its use in applications such as smart window devices. Synthesis of VO2 can be challenging due to the variability of vanadium oxide phases that may be formed. We have employed high-temperature X-ray diffraction (HTXRD) to monitor the reaction process of vanadium oxide precursor powders to form the desired tetragonal VO2 phase. Single-phase tetragonal VO2 was formed within 30 min at 420 °C in flowing N2 gas (~50 ppm O2). The monoclinic-to-tetragonal phase transformation was observed via HTXRD at ~70 °C with the typical ~10 °C hysteresis (i.e. approached from above or below the transition).

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Sharma, Renu. « HREM studies of structure, defects and phase transformation in zirconia and Mn stabilised zirconia ». Proceedings, annual meeting, Electron Microscopy Society of America 48, n^o 4 (août 1990) : 824–25. http://dx.doi.org/10.1017/s0424820100177258.

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Zirconia is known to exist in three different structure types: monoclinic, tetragonal and cubic. Monoclinic is the room temperature form that transforms to tetragonal and finally to cubic at progressively higher temperatures. The monoclinic to tetragonal transformation is reversible, exhibits hysteresis and has been widely studied by thermal analysis, high temperature x-ray diffraction and electron diffraction. This transformation has an undesirable effect on some materials properties. The cubic form of zirconia has been stabilised with yttria, calcia, alumina and magnesia. The decomposition of zirconium carbonate and zirconium manganese carbonate to the respective oxides and their phase tranformation has been studied in situ by electron diffraction and high resolution electron microscopy (HREM) and the results are reported here.The carbonates used in these studies were precipitated from their aqueous solution. Thin crystal fragment were dispersed on holey carbon grids using a suspension in ethanol. A JE0L 4000EX microscope, with double tilt goniometer and on-line Digital MicroVAX II image-analysis system, operating at 400KV, was used for HREM studies.

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Gaillard, Y., M. Anglada et E. Jiménez-Piqué. « Nanoindentation of yttria-doped zirconia : Effect of crystallographic structure on deformation mechanisms ». Journal of Materials Research 24, n^o 3 (mars 2009) : 719–27. http://dx.doi.org/10.1557/jmr.2009.0091.

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This article presents a nanoindentation study of polycrystalline and single crystals of yttria-doped zirconia with both tetragonal and cubic phases. Analysis of the deformation mechanisms is performed by both atomic force microscopy (AFM) and micro-Raman spectroscopy. Phase transformation from tetragonal to monoclinic phase is clearly distinguished on tetragonal crystals, whereas in cubic crystals the plastic deformation seems to be controlled by dislocation nucleation and interactions. AFM observations in tetragonal zirconia grains have shown that both grain size and autocatalytic transformation strongly influence the size of the transformed zone. Furthermore, the martensitic phase transformation seems to be also strongly dependent of the indenter shape. Experimental results suggest that a critical contact pressure is necessary to induce the phase transformation.

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Scardi, P., L. Lutterotti et R. Di Maggio. « XRD Microstructural Characterization of Tetragonal Pure Zirconia Powders Obtained by Controlled Hydrolysis of Zirconium Alkoxides ». Powder Diffraction 6, n^o 1 (mars 1991) : 20–25. http://dx.doi.org/10.1017/s0885715600016808.

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AbstractA new preparation procedure to obtain tetragonal pure zirconia powders is reported together with a detailed analysis of the profile of X-ray Diffraction (XRD) peaks. The crystallization kinetic up to 800°C is described through r.m.s. microstrain and crystallite size distributions. The results of two methods of profile analysis are compared. After thermal treatments up to 100°C the samples of amorphous gel prepared crystallize in the tetragonal structure. The monoclinic phase occurs only above this temperature. Moreover the tetragonal to monoclinic transformation has a strong effect in changing the shape of the distributions. Studying the crystallite size distributions we can infer a critical size of about 300 Å for the tetragonal crystallites to transform. The shape of the mean crystallite of a fully tetragonal sample is also described.

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Takebe, Hiromichi, Tsuneya Okano, Takuya Semba et Kenji Morinaga. « Tetragonal to Monoclinic Transformation in Yttria-Doped Tetragonal Zirconia Polycrystals Examined by Acoustic Microscope ». Journal of the Japan Institute of Metals 54, n^o 12 (1990) : 1358–62. http://dx.doi.org/10.2320/jinstmet1952.54.12_1358.

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Hugo, G. R., Barry C. Muddle et R. H. J. Hannink. « Crystallography of the Tetragonal to Monoclinic Transformation in Ceria-Zirconia ». Materials Science Forum 34-36 (janvier 1991) : 165–69. http://dx.doi.org/10.4028/www.scientific.net/msf.34-36.165.

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Hammond, L. C., et J. L. Cocking. « Rietveld analysis of plasma-sprayed PSZ coatings ». Powder Diffraction 11, n^o 2 (juin 1996) : 75–79. http://dx.doi.org/10.1017/s0885715600009003.

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Rietveld analysis has been successfully used to characterize plasma-sprayed PSZ coatings in a study of the structural stability of 8 wt. % Y2O3–ZrO2 powders and 23 wt. % CeO2/3 wt. % Y2O3–ZrO2, sprayed onto steel substrates. The ceramics were examined in powder form prior to spraying, as-sprayed and after a series of high-temperature soaks at temperatures relevant to those found in heat engines. The study showed that the Y2O3–ZrO2 powders consist of mixtures of the cubic (as the minor phase) and tetragonal (major phase) zirconia and the cubic zirconia polymorph, whereas the as-sprayed materials contain only the tetragonal (major phase) and monoclinic polymorphs indicating that the cubic phase has been lost by transformation. The CeO2–ZrO2 powders consist of a mixture of cubic, tetragonal (major), and monoclinic polymorphs of which the monoclinic phase disappears after plasma spraying. After extended thermal cycling, the Y2O3–ZrO2 coatings did not alter in phase composition whereas the CeO2–ZrO2 coatings became entirely tetragonal.

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Zhang, H., H. L. M. Chang, J. Guo et T. J. Zhang. « Microstructure of epitaxial VO2 thin films deposited on (1120) sapphire by MOCVD ». Journal of Materials Research 9, n^o 9 (septembre 1994) : 2264–71. http://dx.doi.org/10.1557/jmr.1994.2264.

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Epitaxial VO2 thin films grown on (1120) sapphire (α-Al2O3) substrates by MOCVD at 600 °C have been characterized by conventional electron microscopy and high resolution electron microscopy (HREM). Three different epitaxial relationships between the monoclinic VO2 films and sapphire substrates have been found at room temperature: I. (200) [010] monoclinic VO2 ‖ (1120) [0001] sapphire, II. (002) [010] monoclinic VO2 ‖ (1120) [0003] sapphire, and III. (020) [102] monoclinic VO2 ‖ (1120) [0001] sapphire. Expitaxial relationships II and III are equivalent to each other when the film possesses tetragonal structure at the deposition temperature; i.e., they can be described as (010) [100] tetragonal VO2 ‖ (1120) [0001] sapphire and (100) [010] tetragonal VO2 ‖ (1120) [0001] sapphire. HREM image shows that the initial nucleation of the film was dominated by the first orientation relationship, but the film then grew into the grains of the second and the third (equivalent to each other at the deposition temperature) epitaxial relationships. Successive 90°transformation rotational twins around the a-axis are commonly observed in the monoclinic films.

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Rabenberg, L., Josef Fidler et Johannes Bernardi. « Observation and characterization of a twinned monoclinic phase as a product of the solid state decomposition of Nd2Fe14B ». Journal of Materials Research 7, n^o 7 (juillet 1992) : 1762–68. http://dx.doi.org/10.1557/jmr.1992.1762.

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A microtwinned monoclinic phase is observed to occur within the grains of the hard magnetic phase in Nd2Fe14B-based permanent magnet alloys. This phase seems to be the product of a displacive solid state phase transformation of tetragonal Nd2Fe14B, distinguished from Nd2Fe14B by the presence of an ordered substitution into alternating unit cells parallel to the crystallographic c-axis and by a small shear of the type 〈100〉 {011}. The four different orientational variants of this monoclinic phase with respect to the parent tetragonal phase are arranged into two distinct colonies of twin-related plates. The observation that Nd2Fe14B can undergo a displacive solid state transformation has broad implications for the entire field of Nd2Fe14B permanent magnets.

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Hwang, Kyu Hong, et Jong Kook Lee. « Crack Growth by the Isothermal Martensitic Phase Transformation in Tetragonal Zirconia Polycrystals ». Materials Science Forum 738-739 (janvier 2013) : 537–41. http://dx.doi.org/10.4028/www.scientific.net/msf.738-739.537.

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In this study, we investigated the crack nucleation and growth and propagation on the surface of Y-TZP during isothermal phase transformation by low temperature ageing. Crack initiation and growth on the surface of Y-TZP specimen was dependent on the sintered microstructure, i.e, sintered density, grain size, pore structure, residual stress etc.. In the case of Y-TZP with 2mol % yttria content, phase transformation of tetragonal to monoclinic began on the surface and induced a crack nucleation of specimen at the initial stage of low temperature ageing. Most of cracks in 2Y-TZP by low temperature ageing were firstly formed on the surface of specimens (free surface, weak bonding grains, etc.) where the change of strain free energy for a tetragonal to monoclinic transformation was small, and surface cracks grew into the bulk interior through the grain boundaries.

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Kraus, S. « HREM Studies of Interfaces in Zr02/Al203 Ceramics ». Proceedings, annual meeting, Electron Microscopy Society of America 43 (août 1985) : 218–19. http://dx.doi.org/10.1017/s0424820100118011.

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Because of its unusual mechanical and electrolytic properties, zirconia (Zr02) finds a wide variety of uses, such as refractories, oxygen sensors, heaters and extrusion dies. Zr02 exists in three polymorphic forms; the high temperature phase is cubic and is isostructural with CaF2 (fluorite); below 2350°C (in pure ZrO2 ), a tetragonally-distorted version of the fluorite structure exists. At still lower temperature, the tetragonal form (t-Zr02) transforms martensitically to a monoclinic structure (m-Zr02). This t→m transformation gives rise to the phenomenon of transformation toughening in ZrO2 -containing-ceramics, and thus provides ceramics with potential for high

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Fosu, Allen Yushark, Ndue Kanari, Danièle Bartier, James Vaughan et Alexandre Chagnes. « Novel extraction route of lithium from α-spodumene by dry chlorination ». RSC Advances 12, n^o 33 (2022) : 21468–81. http://dx.doi.org/10.1039/d2ra03233c.

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Arata, Anelyse, Tiago Moreira Bastos Campos, João Paulo Barros Machado, Walter Kenji Yoshito, Valter Ussui, Nelson Batista de Lima, Rubens Nisie Tango et Dolores Ribeiro Ricci Lazar. « Aging Behavior of Commercial and Synthesized Dental Y-TZP Ceramics ». Materials Science Forum 820 (juin 2015) : 297–302. http://dx.doi.org/10.4028/www.scientific.net/msf.820.297.

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Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) is used for dental prosthodontics, however, it can present accelerated tetragonal to monoclinic phase transformation in oral environment. The aim of this study was to compare the behavior of a Y-TZP synthesized in laboratory by the coprecipitation method to a commercial Y-TZP, after hydrothermal aging in pressurized reactor (150°C/ 35 hours). The discs were sintered at 1520°C for two hours. The kinetics curve of phase transformation was determined through the data collect by XRD diffractograms treated by the Rietveld method. The experimental and commercial control groups did not present monoclinic phase. After 35 hours of aging, the experimental group presented 69% of monoclinic phase compared to 67% for the commercial group. Scanning electron microscopy and atomic force microscopy images suggested that the commercial group presented heterogeneity of grain size and that the experimental group was more homogeneous. All groups presented superficial degradation process.

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Clarke, D. R., et B. Schwartz. « Transformation toughening of glass ceramics ». Journal of Materials Research 2, n^o 6 (décembre 1987) : 801–4. http://dx.doi.org/10.1557/jmr.1987.0801.

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The utilization of transformation toughening has hitherto been restricted to increasing the fracture resistance of polycrystalline ceramic materials. Although a number of investigators have attempted to extend the concept to toughening glasses and glass ceramics with tetragonal zirconia, no successful reports have been published. It is argued that the approaches employed are inevitably limited primarily because they do not take into account the necessity of nucleating the tetragonal-to-monoclinic transformation away from the crack tip itself. By concentrating on the nucleation event and using standard ceramic processing techniques, it has been demonstated that transformation toughening can be used to increase the toughness of glass-ceramic materials, and this approach is illustrated by increasing the fracture toughness of a cordierite glass ceramic.

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Rawat, Mukesh, Arkaprava Das, D. K. Shukla, Parasmani Rajput, A. Chettah, D. M. Phase, R. C. Ramola et Fouran Singh. « Micro-Raman and electronic structure study on kinetics of electronic excitations induced monoclinic-to-tetragonal phase transition in zirconium oxide films ». RSC Advances 6, n^o 106 (2016) : 104425–32. http://dx.doi.org/10.1039/c6ra14199d.

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Monoclinic-to-tetragonal phase transformation (PT) in sputtering grown zirconium oxide (ZrO₂) films on silicon substrates by electronic excitation (EE) induced by swift heavy ion (SHI) irradiation is reported.

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Collins, David E., et Keith J. Bowman. « Influence of atmosphere on crystallization of zirconia from a zirconium alkoxide ». Journal of Materials Research 13, n^o 5 (mai 1998) : 1230–37. http://dx.doi.org/10.1557/jmr.1998.0175.

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Dibutoxybis (acetylacetonato) zirconium, a difunctional zirconium alkoxide, was polymerized at 130 °C for 5 h in vacuo to produce oligomers that could be pyrolyzed to form a tetragonal zirconia (t-ZrO2), metastable at room temperature. This metastable phase was retained considerably below the equilibrium transformation temperature (∼1200 °C) without the use of dopants. Comparative pyrolysis of the oligomers between 600 and 900 °C in either flowing O2 or N2 for processing times under 12 h indicated t-ZrO2 nucleated first. Pyrolysis in oxygen facilitated transformation to the monoclinic symmetry, whereas pyrolysis in nitrogen demonstrated retention of the tetragonal phase. The formation of oxygen vacancies during pyrolysis, their role in stabilizing the metastable tetragonal phase, and contributions of O2 and crystallite size in the polymorphic transformation are discussed.

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Ma, Yuxiang, Erich H. Kisi, Shane J. Kennedy et Andrew J. Studer. « Tetragonal-to-Monoclinic Transformation in Mg-PSZ Studied byin SituNeutron Diffraction ». Journal of the American Ceramic Society 87, n^o 3 (mars 2004) : 465–72. http://dx.doi.org/10.1111/j.1551-2916.2004.00465.x.

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Chevalier, Jérôme, Laurent Gremillard, Anil V. Virkar et David R. Clarke. « The Tetragonal-Monoclinic Transformation in Zirconia : Lessons Learned and Future Trends ». Journal of the American Ceramic Society 92, n^o 9 (septembre 2009) : 1901–20. http://dx.doi.org/10.1111/j.1551-2916.2009.03278.x.

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Xie, Shuibo, Enrique Iglesia et Alexis T. Bell. « Water-Assisted Tetragonal-to-Monoclinic Phase Transformation of ZrO2at Low Temperatures ». Chemistry of Materials 12, n^o 8 (août 2000) : 2442–47. http://dx.doi.org/10.1021/cm000212v.

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Navruz *, N. « Crystallography of the tetragonal-to-monoclinic phase transformation in ceria-zirconia ». Phase Transitions 78, n^o 7-8 (septembre 2005) : 539–45. http://dx.doi.org/10.1080/01411590500158770.

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Ramamoorthy, R., S. Ramasamy et D. Sundararaman. « Annealing effects on phase transformation and powder microstructure of nanocrystalline zirconia polymorphs ». Journal of Materials Research 14, n^o 1 (janvier 1999) : 90–96. http://dx.doi.org/10.1557/jmr.1999.0015.

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Nanocrystalline zirconia powders in pure form and doped with yttria and calcia were prepared by the precipitation method. In the as-prepared condition, all the doped samples show only monoclinic phase, independent of the dopants and dopant concentration. On annealing the powders at 400 °C and above, in the case of 3 and 6 mol% Y2O3 stabilized ZrO2 (3YSZ and 6YSZ), the monoclinic phase transforms to tetragonal and cubic phases, respectively, whereas in 3 and 6 mol% CaO stabilized ZrO2 (3CSZ and 6CSZ), the volume percentage of the monoclinic phase gradually decreases up to the annealing temperature of about 1000 °C and then increases for higher annealing temperatures. The presence of monoclinic phase in the as-prepared samples of doped zirconia has been attributed to the lattice strain effect which results in the less symmetric lattice. For the annealing temperatures below 1000 °C, the phenomenon of partial stabilization of the tetragonal phase in 3CSZ and 6CSZ can be explained in terms of the grain size effect. High resolution transmission electron microscopy (HRTEM) observations reveal the lattice strain structure in the as-prepared materials. The particles are found to be a tightly bound aggregate of small crystallites with average size of 10 nm. The morphology of the particles is observed to be dependent on the dopants and dopant concentration.

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Mommer, Niels, Theresa Lee et John A. Gardner. « Stability of monoclinic and tetragonal zirconia at low oxygen partial pressure ». Journal of Materials Research 15, n^o 2 (février 2000) : 377–81. http://dx.doi.org/10.1557/jmr.2000.0059.

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We have found that both tetragonal and monoclinic zirconia annealed at temperaturess in the range of 1100 to 1300 °C in atmospheres of low oxygen partial pressures (down to 10−26 Pa) transform slowly to an apparently cubic phase. The transformation can be reversed by increasing the oxygen partial pressure sufficiently, i.e., exposing the sample to air again. These observations were made by 111In/Cd perturbed angular correlation (PAC) measurements of undoped zirconia samples. Upon annealing under various reducing atmospheres PAC spectra show a steadily increasing fraction of Cd probe atoms in a locally cubic environment with the fraction of probe atoms in tetragonal or monoclinic sites decreasing accordingly.

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Manriquez, M. E., M. Picquart, X. Bokhimi, T. López, P. Quintana et J. M. Coronado. « X-Ray Diffraction, and Raman Scattering Study of Nanostructured ZrO2-TiO2 Oxides Prepared by Sol–Gel ». Journal of Nanoscience and Nanotechnology 8, n^o 12 (1 décembre 2008) : 6623–29. http://dx.doi.org/10.1166/jnn.2008.18436.

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In the present work, we study the phase composition of ZrO2-TiO2 system by means of XRD and Raman spectroscopy, using also TG-ATD, and N2 adsorption isotherms as complementary characterization techniques. TiO2-ZrO2 samples of selected compositions (0, 10, 90, 50 and 100% in weight of TiO2) were prepared by sol–gel method and annealed at three different temperatures (400, 600 and 800 °C). Structural characterization reveals that only the pure oxides are crystalline at 400 °C: TiO2 as anatasa with a minor brookite component, and ZrO2 as a mixture of tetragonal (majority) and monoclinic phases. Following the 600 °C calcination, the TiO2-ZrO2 50–50% sample forms the ZrTiO4 mixed oxide, although this materials remains partly amorphous. In contrast, samples with higher and lower TiO2 content form solid solutions with, respectively, anatasa and tetragonal ZrO2 structures. Zirconium incorporation into the TiO2 lattice leads to the expansion of the unit cell parameters, and it stabilizes the anatase phase, hindering its transformation into rutile. Similarly, dissolving titanium atoms into the ZrO2 structure delays the transformation from the tetragonal to the monoclinic polymorph.

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Yamada, Kiyotaka, et Giuseppe Pezzotti. « Environmental Phase Stability of Ceramics Composite for Hip Prostheses in Presence of Surface Damage ». Key Engineering Materials 361-363 (novembre 2007) : 783–86. http://dx.doi.org/10.4028/www.scientific.net/kem.361-363.783.

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Alumina matrix composite (AMC) has been widely used for artificial hip and knee joints because of its phase stability in human body and its excellent wear resistance. The excellent mechanical properties of strength and fracture toughness of zirconia materials are well known to be closely related to stress-induced transformation from the tetragonal to the monoclinic phase, which is accompanied with 4% volume increase of the zirconia crystal cell. However, it is also to be considered that the material is prone to low temperature aging degradation (LTAD) under hydrothermal environment, like in the human body. This LTAD is influenced by the tetragonal to the monoclinic (t-m) phase transformation. T-m transformation also induces the formation of microcracks at the material surface, and an increase in surface. Microcracking leads to a decrease of mechanical properties, and could explain the failure of implants after some years in vivo [1, 2] .Therefore, it is very important to study how to prevent phase transformation in zirconia components. Transformed monoclinic zirconia percentage can be experimentally measured by Raman spectroscopy and the residual stress distribution, which is related to phase transformation, can be determined by a non-destructive piezo-spectroscopic analysis. In this paper, we attempted to evaluate it from both stress and mechanical properties points of view by confocal Raman and fluorescence spectroscopy.

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Candido, LM, LMG Fais, EB Ferreira, SG Antonio et LAP Pinelli. « Characterization of a Diamond Ground Y-TZP and Reversion of the Tetragonal to Monoclinic Transformation ». Operative Dentistry 42, n^o 4 (1 juillet 2017) : 407–17. http://dx.doi.org/10.2341/16-196-l.

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SUMMARY Purpose: To characterize the surface of an yttria-stabilized zirconia (Y-TZP) ceramic after diamond grinding in terms of its crystalline phase, morphology, mean roughness (Ra), and wettability as well as to determine a thermal treatment to reverse the resulting tetragonal to monoclinic (t-m) transformation. Methods and Materials: Y-TZP specimens were distributed into different groups according to the actions (or no action) of grinding and irrigation. Grinding was accomplished using a diamond stone at a low speed. The samples were characterized by x-ray diffraction (XRD), scanning electron microscopy, goniometry, and profilometry. In situ high-temperature XRD was used to determine an annealing temperature to reverse the t-m transformation. Ra was submitted to the Kruskal-Wallis test, followed by the Dunn test (α=0.05). The volume fraction of the monoclinic phase and contact angle were submitted to one-way analysis of variance, followed by the Tukey test (α=0.05). Results: Monoclinic zirconia was observed on the surface of samples after dry and wet grinding with a diamond stone. The volume fraction of the monoclinic phase was smaller on the dry ground samples (3.6%±0.3%) than on the wet ground samples (5.6%±0.3%). High-temperature XRD showed reversion of the t-m phase transformation, which started at 700°C and completed at 800°C in a conventional oven. Conclusions: Grinding with a diamond stone partially transformed the crystalline phase on the surface of a Y-TZP ceramic from tetragonal to monoclinic zirconia while simultaneously increasing the surface roughness and wettability. The t-m transformation could be reversed by heat treatment at 800°C or 900°C for 60 minutes or 1000°C for 30 minutes.

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Mecartney, M. L., et M. Rühle. « In situ transmission electron microscopy observations of the monoclinic to tetragonal phase transformation in tetragonal ZrO2 ». Acta Metallurgica 37, n^o 7 (juillet 1989) : 1859–63. http://dx.doi.org/10.1016/0001-6160(89)90070-9.

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Hugo, G. R., B. C. Muddle et R. H. J. Hannink. « An electron diffraction study of the tetragonal— monoclinic transformation in 12 mole% ceria-zirconia ». Proceedings, annual meeting, Electron Microscopy Society of America 48, n^o 4 (août 1990) : 1054–55. http://dx.doi.org/10.1017/s0424820100178409.

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The tetragonal (t) ↔ monoclinic (m) transformation occurring in 12 mole% CeO2-ZrO2 is a source of significant transformation plasticity and transformation toughening in this ceramic material. The t↔m transformation is martensitic in nature and a quantitative understanding of the transformation plasticity and transformation toughening requires that the crystallography of this martensitic transformation be understood in detail. Crystallographic characteristics of a martensitic phase transformation are:1. the existence of a unique lattice correspondence between the phases, which specifies the directions in the product crystal lattice into which any given directions in the parent crystal lattice are transformed, 2. a fixed orientation relationship preserved between parent and product phases, and 3. the orientation of the habit plane or interface plane between the parent and product phases.For the t↔m transformation occurring in ceria-zirconia, three possible lattice correspondences are plausible.

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Shimozono, Takayoshi, Junji Ikeda et Giuseppe Pezzotti. « Evaluation of Transformation Zone Around Propagating Cracks in Zirconia Biomaterials Using Raman Microprobe Spectroscopy ». Key Engineering Materials 309-311 (mai 2006) : 1207–10. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.1207.

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Structural reliability, biocompatibility and bioinertness are fundamental prerequisites for bioceramics used in artificial hip and knee joints. Among structural properties, superior fracture toughness is necessary for guaranteeing high reliability during implantation lifetime. Bioinert ceramics employed in artificial joints are mainly limited to alumina and zirconia materials. In this paper, the critical crack-tip stress intensity factor, KI0, and the tetragonal-to-monoclinic phase-transformation behavior of a 3 mol % Y2O3-doped tetragonal ZrO2 polycrystals (3Y-TZP) were studied as a function of grain size. 3Y-TZP’s with four different grain sizes were prepared and the size and morphology of the monoclinic transformation zone generated around the tip of an indentation crack were analyzed by quantitative Raman microprobe spectroscopy. The stress intensity factor, KI0, was evaluated by the crack opening displacement (COD) method using a recently proposed equation for calculating the compliance of an indentation crack.

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Vermaut, Philippe, Anna Manzoni, Anne Denquin, Frédéric Prima et Richard Portier. « Unexpected Constrained Twin Hierarchy in Equiatomic Ru-Based High Temperature Shape Memory Alloy Martensite ». Materials Science Forum 738-739 (janvier 2013) : 195–99. http://dx.doi.org/10.4028/www.scientific.net/msf.738-739.195.

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Among the different systems for high temperature shape memory alloys (SMA’s), equiatomic RuNb and RuTa alloys demonstrate both shape memory effect (SME) and MT temperatures above 800°C. Equiatomic compounds undergo two successive martensitic transformations, β (B2) → β’ (tetragonal) → β’’ (monoclinic), whereas out of stoechiometry alloys exhibit a single transition from cubic to tetragonal. In the case of two successive martensitic transformations, we expect to have a finer microstructure of the second martensite because it is supposed to develop inside the smallest twin elements of the former one. In equiatomic Ru-based alloys, if the first martensitic transformation is “normal”, the second one gives different unexpected microstructures with, for instance, twins with a thickness which is larger than the smallest spacing between twin variants of the first martensite. In fact, the reason for this unexpected hierarchy of the twins size is that the second martensitic transformation takes place in special conditions: geometrically, elastically and crystallographically constrained.

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Frigan, Chevalier, Zhang et Spies. « Is a Zirconia Dental Implant Safe When It Is Available on the Market ? » Ceramics 2, n^o 4 (12 octobre 2019) : 568–77. http://dx.doi.org/10.3390/ceramics2040044.

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The market share of zirconia (ZrO2) dental implants is steadily increasing. This material comprises a polymorphous character with three temperature-dependent crystalline structures, namely monoclinic (m), tetragonal (t) and cubic (c) phases. Special attention is given to the tetragonal phase when maintained in a metastable state at room temperature. Metastable tetragonal grains allow for the beneficial phenomenon of Phase Transformation Toughening (PTT), resulting in a high fracture resistance, but may lead to an undesired surface transformation to the monoclinic phase in a humid environment (low-temperature degradation, LTD, often referred to as ‘ageing’). Today, the clinical safety of zirconia dental implants by means of long-term stability is being addressed by two international ISO standards. These standards impose different experimental setups concerning the dynamic fatigue resistance of the final product (ISO 14801) or the ageing behavior of a standardized sample (ISO 13356) separately. However, when evaluating zirconia dental implants pre-clinically, oral environmental conditions should be simulated to the extent possible by combining a hydrothermal treatment and dynamic fatigue. For failure analysis, phase transformation might be quantified by non-destructive techniques, such as X-Ray Diffraction (XRD) or Raman spectroscopy, whereas Scanning Electron Microscopy (SEM) of cross-sections or Focused Ion Beam (FIB) sections might be used for visualization of the monoclinic layer growth in depth. Finally, a minimum load should be defined for static loading to fracture. The purpose of this communication is to contribute to the current discussion on how to optimize the aforementioned standards in order to guarantee clinical safety for the patients.

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Zhan, Zhaoqi, et Hua C. Zeng. « Metastability of tetragonal ZrO2 derived from Zr-n-propoxide-acetylacetone-water-isopropyl alcohol ». Journal of Materials Research 13, n^o 8 (août 1998) : 2174–83. http://dx.doi.org/10.1557/jmr.1998.0304.

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ZrO2 nanopowders derived from zirconium n-propoxide [Zr(OC3H7)4]-acetylacetone-water-isopropanol have been investigated with respect to their tetragonal metastability on heating-cooling processes. The transformation temperature of metastable tetragonal to monoclinic (t′ → m) phase is found to be governed by ultimate firing temperature, time, and atmospheres employed. Crystallite growth is fastened with increase in calcination temperatures over 1000–1400 °C, and the t′ → m transformation temperature is correlated linearly with crystallite size in the studied range of 12–20 nm. Heating in an oxygen environment increases the size of the final crystallites and hence the rate of the t′ → m transformation. It is revealed that the t′ → m transformation temperature depends largely on the heating atmosphere, but only weakly on the cooling one. Based on the findings of this work, surface oxygen deficiencies are attributed to be responsible for low-temperature tetragonal metastability. A crystallite growth model to explain the decline of t′-ZrO2phase is proposed. Kinetic and thermodynamic factors are also discussed in connection with the existing theories of tetragonal metastability.

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Coll, R., J. Bonastre, J. Saurina, J. J. Suñol, L. Escoda et B. Hernando. « Martensitic Transformation in Mn-Ni-Sn Alloys ». Materials Science Forum 738-739 (janvier 2013) : 468–72. http://dx.doi.org/10.4028/www.scientific.net/msf.738-739.468.

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In this work, we analyze two Mn50Ni50-xSnx alloys with Sn content i.e., x = 5 and 7.5 respectively. These alloys are produced as ribbon-shape by melt spinning. Their structural transformation is checked by calorimetry. Martensitic transformation temperatures of these alloys strongly depend on the composition. From X-ray diffraction analysis, the 14M monoclinic phase is the main phase in both alloys, but in the alloy Sn5 appears a minor tetragonal phase too.

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Uchikoshi, T., Y. Sakka, K. Ozawa et K. Hiraga. « Preparation of fine-grained monoclinic zirconia ceramics by colloidal processing ». Journal of Materials Research 13, n^o 4 (avril 1998) : 840–43. http://dx.doi.org/10.1557/jmr.1998.0110.

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Fine-grained monoclinic zirconia ceramic was made from well-dispersed zirconia sol prepared by the hydrolysis of zirconium chloride oxide octahydrate. Dechlorinated and concentrated zirconia sol was consolidated by pressure filtration. The relative green density of the compact was improved by the following cold isostatic pressing treatment at 400 MPa. The compact was densified by pressureless sintering to >98% of theoretical density in air at 1100 °C, which is lower than that of monoclinic to tetragonal transformation of pure zirconia. The average grain size of the sintered monoclinic zirconia ceramics was 92 nm.

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MUDDLE, B. C., et R. H. J. HANNINK. « Crystallography of the Tetragonal to Monoclinic Transformation in MgO-Partially-Stabilized Zirconia ». Journal of the American Ceramic Society 69, n^o 7 (juillet 1986) : 547–55. http://dx.doi.org/10.1111/j.1151-2916.1986.tb04791.x.

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Jian, Li, et C. M. Wayman. « Monoclinic-to-Tetragonal Phase Transformation in a Ceramic Rare-Earth Orthoniobate, LaNbO4 ». Journal of the American Ceramic Society 80, n^o 3 (mars 1997) : 803–6. http://dx.doi.org/10.1111/j.1151-2916.1997.tb02905.x.

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Rauchs, G., T. Fett, D. Munz et R. Oberacker. « Tetragonal-to-monoclinic phase transformation in CeO2-stabilised zirconia under uniaxial loading ». Journal of the European Ceramic Society 21, n^o 12 (octobre 2001) : 2229–41. http://dx.doi.org/10.1016/s0955-2219(00)00258-2.

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Rauchs, G., T. Fett, D. Munz et R. Oberacker. « Tetragonal-to-monoclinic phase transformation in CeO2-stabilized zirconia under multiaxial loading ». Journal of the European Ceramic Society 22, n^o 6 (juin 2002) : 841–49. http://dx.doi.org/10.1016/s0955-2219(01)00384-3.

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