Monoclinic-tetragonal Transition Research Articles

Machine learning potential for Ab Initio phase transitions of zirconia

Zirconia has been extensively used in aerospace, military, biomedical and industrial fields due to its unusual combination of high mechanical, electrical and thermal properties. However, the fundamental and critical phase transition process of zirconia has not been well studied because of its difficult first-order phase transition with formidable energy barrier. Here, we generated a machine learning interatomic potential with ab initio accuracy to discover the mechanism behind all kinds of phase transition of zirconia at ambient pressure. The machine learning potential precisely characterized atomic interactions among all zirconia allotropes and liquid zirconia in a wide temperature range. We realized the challenging reversible first-order monoclinic-tetragonal and cubic-liquid phase transition processes with enhanced sampling techniques. From the thermodynamic information, we gave a better understanding of the thermal hysteresis phenomenon in martensitic monoclinic-tetragonal transition. The phase diagram of zirconia from our machine learning potential based molecular dynamics simulations corresponded well with experimental results.

Neural-network-backed effective harmonic potential study of the ambient pressure phases of hafnia

Machine learning methods, and in particular neural-network force fields (NNFF), are bridging the gap between macroscopically relevant parameters and quantum mechanical simulations. This work describes an NNFF training strategy and uses it as the back end for an effective harmonic potential study of phase transitions in hafnia. While good agreement with experiment is found regarding the monoclinic-tetragonal transition, the commonly assumed transition to a Fm$\overline{3}$m cubic phase is found to be unlikely for the stoichiometric material

Керамический композит на основе диоксида циркония, армированный одностенными углеродными нанотрубками

Исследовано влияние относительного содержания одностенных углеродных нанотрубок (ОУНТ) на уплотнение, фазовый состав, микроструктуру и физико-механические свойства композитов на основе стабилизированного иттрием диоксида циркония, полученных электроимпульсным плазменным спеканием. Обнаружено, что в композитах, содержащих 0.1 и 0.5 мас. % ОУНТ, наблюдается существенное повышение относительной плотности: с 98.26 до 99.98%. Установлено, что ОУНТ частично ограничивают моноклинно-тетрагональный переход при высокотемпературной обработке диоксида циркония. Трещиностойкость композита с 1 мас. % ОУНТ возрастает на 38% по сравнению с керамикой без добавок.

Low scan rate DSC study of the monoclinic-tetragonal transition in zirconia

The effect of heating and cooling rates on the DSC (differential scanning calorimetry) heat flux peak of the monoclinic-tetragonal transition of zirconia was investigated in the 0.4–20 °C/min scan rate range. While the peak position, shape and area at high to moderate scan rates are consistent with existing literature data, a ‘step change’ (i.e., a peak-less baseline shift) was observed for the extremely slow heating rate of 0.4 °C/min. As expected, peak profiles in the heating and cooling transitions are markedly different, the peak shape being strongly asymmetrical for the t → m transition, but very closely symmetrical for the m → t transition. As the cooling rate is lowered, the t → m peak is increasingly splitted into multiple components, whose individual properties have been fitted using Gamma distribution functions.

Effect of Hydrostatic Pressure on the Dielectric Properties of PMN-0.31PT Single Crystal

[Pb(Mg 1/3 Nb 2/3 )O 3 ] 0.69 (PbTiO 3 ) 0.31 single crystal of composition close to the morphotropic phase boundary has been studied by dielectric spectroscopy in the frequency range of 1–1000 kHz under hydrostatic pressure (p) up to 0.6 GPa. At ambient pressure two successive phase transitions have been observed: the monoclinic-tetragonal transition at T 1 = 346 K and the transition from the ferroelectric tetragonal to the cubic relaxor phase at T C = 415.7 K. At elevated pressures the temperature range of the ferroelectric tetragonal phase diminished, while the relaxor phase evolved. The p-T phase diagram shows that pressure decreases linearly T 1 and T C , as well as the temperature T m of the relaxor peak, but with different slopes: dT 1 / dp = −(2.6 ± 1.6) K/GPa, dT C/ dp = −(55.5 ± 0.2) K/GPa and dT m (10 kHz)/ dp = −(48.7 ± 1.0) K/GPa.

2322 ナノ結晶ジルコニアの超塑性的圧縮変形(S32-2 セラミックスおよびセラミックス系複合材料(2),S32 セラミックスおよびセラミックス系複合材料)

The deformation behavior of nanocrystalline monoclinic ZrO_2 polycrystals (nano MZP) was studied at 1273-1373K in compression tests. The deformation of nano MZP was characterized by stress exponent n=2.5 and apparent activation energy Q=350kJ/mol. The strain rate of nano MZP was faster than that of Y_2O_3-stabilized tetragonal ZrO_2 (Y-TZP) at temperatures lower than the monoclinic-tetragonal transition temperature. The strain rate of MZP gradually approached to that of Y-TZP as the temperature increased to the transition temperature.

First-principles characterization of a heteroceramic interface:ZrO2(001)deposited on anα−Al2O3(11¯02)substrate

We have studied an alumina/zirconia interface using the all-electron projector augmented wave formalism within density functional theory. We present the electronic, structural, and energetic properties of the ${\mathrm{ZrO}}_{2}(001)/\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(11\ifmmode\bar\else\textasciimacron\fi{}02)$ interface as well as of the free $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(11\ifmmode\bar\else\textasciimacron\fi{}02)$ and ${\mathrm{ZrO}}_{2}(001)$ surfaces. We find that the generalized gradient correction significantly lowers the oxide surface energies, compared to values obtained by the local density approximation. The monoclinic-tetragonal transition in ${\mathrm{ZrO}}_{2}(001)$ thin films is discussed as well as strain effects involved in the interface formation. The stoichiometric alumina/zirconia interface is found to be weakly bonded, regardless of the film thickness, and the ${\mathrm{ZrO}}_{2}(001)/\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(11\ifmmode\bar\else\textasciimacron\fi{}02)$ interface has a rather epitaxial character, due to a low lattice mismatch of $\ensuremath{\sim}4%.$ The impact of such weak interactions on ceramic coating stability is discussed.

Micro-raman studies on materials based on zirconium dioxide

Micro-Raman studies have been made on zirconium dioxide ceramics and crystals by the use of argon and helium-neon lasers. The Raman results for the crystals are appreciably affected by the wavelength, which is due to a luminescence spectrum more intense than the background (this is not usually characteristic of zirconium dioxide ceramics). When a crystal is indented, the monoclinic phase is detected only near the edges of the indent, so that process cannot be the cause of the rise in the surface around the indent. It is concluded that the crystals differ from the ceramics in that the monoclinic-tetragonal transition is not the mechanism that governs the mechanical behavior.

単斜型ジルコニアの耐火物的応用

It is widely believed that ZrO2 refractory can not be available without being stabilized or partially stabilized because of its large volume change derived from its monoclinic-tetragonl-cubic transition. This concept can generally be acceptable in fired refractory where monoclinic-tetragonal transition occures reciprocatingly during firing process. On the contrary, the concept can not necessary be acceptable in fusion cast refractory because aforementioned transition can only once be experienced unreciprocatingly during cooling process from melt to solid and also this transition is not accompanied with volume contraction causing tensile stress. Authors, on the basis of up-dated data and informations, give a commentary on the monoclinic ZrO2 refractory which is now widely applied in glass industries.

Texture on Ground, Fractured, and Aged Y-TZP Surfaces

ABSTRACTThe phase composition of Y-TZP surfaces has been shown to vary greatly depending on the thermo-mechanical history of the surface. The orientation of these different phases in the surface region is not always random. There is speculation that the alignment of the tetragonal phase before fracturing may play a part in increasing the toughness of these materials. This article deals with an X-ray diffraction analysis of various Y-TZP surfaces with special emphasis on the texture of the different phases. Surfaces which have been ground (and polished), fractured, and aged (200°C) have been examined. In all cases, the monoclinic component that was formed was strongly oriented. The tetragonal phase may or may not be oriented depending on surface treatment. Annealing above the monoclinic-tetragonal transition temperature had little effect on the tetragonal orientation in most cases. Samples fractured at 1000°C have no unusual orientation on the fracture faces.

Radiation-induced Phase Transformations in NdNb1−xVxO4

Abstract When NdNb1−xVxO4 compounds were exposed to a fast neutron dose of 6.6×1018 nvt, their monoclinictetragonal transition temperatures were lowered; particularly the transition temperature for the compound with x=0.3 was lowered to a temperature below room temperature. The lowering of the transition temperatures was greater for samples containing more V5+ ions. Although the present work does not fully reveal why neutronirradiation lowers the transition temperature, it does show that neither the internal stress due to radiation damage nor the change in valency state of Nb5+ or Nd3+ lowers the transition temperature.

A neutron diffraction study of room-temperature monoclinic Kd 2PO 4

The crystal structure of the room-temperature monoclinic phase of high-deuteration DKDP has been determined by neutron diffraction measurements on a single crystal. The arrangement of K, P and O atoms is essentially that determined previously by X-ray diffraction: the D atoms have been located. It is confirmed that the monoclinic-tetragonal transition is a reconstructive one involving large (> 1 Å) relative atomic displacements.

Effect of Pressure on Monoclinic‐Tetragonal Transition of Zirconia; Thermodynamics

Journal of the American Ceramic SocietyVolume 45, Issue 12 p. 612-613 Effect of Pressure on Monoclinic-Tetragonal Transition of Zirconia; Thermodynamics E. DOW WHITNEY, E. DOW WHITNEYSearch for more papers by this author E. DOW WHITNEY, E. DOW WHITNEYSearch for more papers by this author First published: December 1962 https://doi.org/10.1111/j.1151-2916.1962.tb11072.xCitations: 53 The writer is senior research associate, Basic Research Branch, Research and Development Division, The Carborundum Company, Niagara Falls, New York. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume45, Issue12December 1962Pages 612-613 RelatedInformation

Monoclinic‐Tetragonal Transition of Zirconia

Journal of the American Ceramic SocietyVolume 44, Issue 3 p. 147-148 Monoclinic-Tetragonal Transition of Zirconia C. T. LYNCH, C. T. LYNCHSearch for more papers by this authorF. W. VAHLDIEK, F. W. VAHLDIEKSearch for more papers by this authorL. B. ROBINSON, L. B. ROBINSONSearch for more papers by this author C. T. LYNCH, C. T. LYNCHSearch for more papers by this authorF. W. VAHLDIEK, F. W. VAHLDIEKSearch for more papers by this authorL. B. ROBINSON, L. B. ROBINSONSearch for more papers by this author First published: March 1961 https://doi.org/10.1111/j.1151-2916.1961.tb13732.xCitations: 34 The writers are, respectively, research chemist, research chemist, and research assistant, Ceramics and Graphite Branch, Metals and Ceramics Laboratory, Materials Central, Directorate of Advanced Systems Technology, Wright Air Development Division, Air Research and Development Command, United States Air Force, Wright-Patterson Air Force Base, Ohio. This work is taken in part from a Wright Air Development Division Technical Report, No. 60–705, by the writers, based on a project initiated in the Materials Central. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume44, Issue3March 1961Pages 147-148 RelatedInformation