Journal ArticleDOI
Structural analysis of orthorhombic hafnia by neutron powder diffraction
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In this article, the crystal structure of orthorhombic HfO2 synthesized at 600°C and 6 GPa was investigated by a time-of-flight neutron powder diffraction experiment.Abstract:
The crystal structure of orthorhombic HfO2 synthesized at 600°C and 6 GPa was investigated by a time-of-flight neutron powder diffraction experiment. Rietveld analysis of these data revealed that the space group of this phase is Pbca. The refined lattice parameters are a0= 1.00177, b0= 0.52276, and c0= 0.50599 nm. The structure is derived from a distorted fluorite (CaF2) structure by a b-glide parallel to the a-axis. The hafnium atom is in seven-fold coordination. The structure of orthorhombic HfO2 is found to be the same as that of an orthorhombic ZrO2, which occurs under high pressure above 3 GPa.read more
Citations
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The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model
TL;DR: In this paper, the structural, thermal, and dielectric properties of the ferroelectric phase of HfO2, ZrO2 and Hf0.5O2 are investigated with carefully validated density functional computations.
Journal ArticleDOI
The Origin of Ferroelectricity in Hf$_{x}$ Zr$_{1-x}$ O$_2$: A Computational Investigation and a Surface Energy Model
TL;DR: In this article, the structural, thermal, and dielectric properties of the ferroelectric phase of HfO$_2, ZrO_2$ and Hf$_{0.5}$ Zr$_{1-\chi}$ O$-2$ (HZO) are investigated with carefully validated density functional computations.
Journal ArticleDOI
Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature
O. Ohtaka,Hiroshi Fukui,Taichi Kunisada,Tomoyuki Fujisawa,Ken-ichi Funakoshi,Wataru Utsumi,Tetsuo Irifune,Koji Kuroda,Takumi Kikegawa +8 more
TL;DR: In this paper, X-ray in situ observations of HfO 2 under high pressure and high temperature have been performed to investigate its phase relations and compression behavior, and orthorhombic phase (orthol) is stable from 4 to 14.5 GPa below 1250°-1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of orthO 2 above these temperatures.
Journal ArticleDOI
Electronic properties of hafnium oxide: A contribution from defects and traps
Vladimir A. Gritsenko,Vladimir A. Gritsenko,Timofey V. Perevalov,Timofey V. Perevalov,Damir R. Islamov,Damir R. Islamov +5 more
TL;DR: In this article, the role of oxygen vacancies as traps that facilitate charge transport in hafnium oxide films is discussed, and it is shown that the electrical conductivity of the material is controlled by the phonon-assisted tunnelling of charge carriers between traps that were identified as oxygen vacancies.
References
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Journal ArticleDOI
Effect of stress-induced phase transformation on the properties of polycrystalline zirconia containing metastable tetragonal phase
TL;DR: In this article, a stress-induced phase transformation in the metastable tetragonal phase of polycrystalline zirconia was shown to increase the strength and grain size.
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Crystal Structure of Monoclinic Hafnia and Comparison with Monoclinic Zirconia
Robert Ruh,Peter W. R. Corfield +1 more
TL;DR: In this article, the crystal structure of monoclinic HfO2 was determined using Weissenberg techniques using a needle-like single crystal which was grown from a lithium molybdate melt.
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Pressure‐Temperature Phase Diagram of Zirconia
TL;DR: In this article, the phase diagram of zirconia was determined by optical microscopy and X-ray diffraction techniques using a diamond anvil pressure cell, and the initial transformation pressure for the monoclinic-tI-tII transition on a virgin ZrO/sub 2/ crystal can be as high as 4.4 GPa; on subsequent cycling the transition pressure ultimately lowers to 3.29 + or 0.06 GPa.
Journal ArticleDOI
Rietveld analysis of powder patterns obtained by TOF neutron-diffraction using cold neutron sources
TL;DR: In this paper, a profile shape function is implemented which is optimized for a solid-methane moderator at 20'K and the results of Rietveld refinements of Si and α-Al2O3 show that the profile shape functions fit neutron diffraction patterns taken on the HRP very well, and that very precise crystal-structure parameters can be obtained with this program.
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In situ determination of crystal structure for high pressure phase of ZrO 2 using a diamond anvil and single crystal X-ray diffraction method
TL;DR: In this paper, the crystal structure of a synthetic ZrO2 has been studied in situ up to 51 kbar at room temperature, where the directions of the b and c axes are preserved through the transition and the transformation is displacive.