Angular-dispersive x-ray in situ powder-diffraction experiments have been performed on pure zirconia, ${\mathrm{ZrO}}_{2}$, at room temperature under high pressure up to 50 GPa. Under increasing four phases were successively encountered: baddeleyite (monoclinic, P${2}_{1}$/c) from normal about 10 GPa, orthorhombic-I (Pbca) 25 orthorhombic-II 42 and orthorhombic-III above The unit-cell parameters the volume determined as a function of pressure. bulk moduli two lower calculated using Birch's...

The crystal structures of the cotunnite‐type phases (space group, Pnam, Z = 4) pure zirconia and hafnia prepared under high‐temperature, high‐pressure conditions in a multianvil device were refined by time‐of‐flight neutron powder diffraction. both compounds are very similar nine polyhedral metal‐oxygen distances range from 2.133(1) to 2.546(1) Å ZrO 2 2.121(1) 2.535(2) HfO . Raman spectra resemble one another strongly consistent with structure. These results confirm that undergo transitions...

The phase transformations and pressure-volume dependence of ${\mathrm{HfO}}_{2}$ have been investigated at room temperature by angle-dispersive powder x-ray diffraction under high pressure to 50 GPa in a diamond anvil cell. transformation from the monoclinic I (baddeleyite) orthorhombic II was observed around 10 GPa. This is stable up 26 where it transforms new III with another unit At about 42 GPa, third transition occurs IV tetragonal symmetry. dependences cell parameters volume...

In this study, we have investigated the sintering of mullite by three different methods: (i) reaction thermal decomposition kaolinite, followed with alumina; (ii) solid state pure silica and (iii) commercial electrofused powder. all cases, mixtures powders were compacted dry pressing sintered at temperatures between 1000°C 1600°C using a resistive furnace. The phase identification was performed X-ray difractometry, microstructure studied scanning electron microscopy. Density porosity...

Abstract Lithium disilicate glasses and glass–ceramics are good potential candidates for biomedical applications, solid‐state batteries, serve as models of nucleation crystal growth. Moreover, these exhibit a phase separation that influences their crystallization behavior. The atomistic mechanisms the pressure dependence unclear so far. Here, we used molecular dynamics simulations supported by experiments to assess spatial heterogeneity lithium prepared under pressure. We show glass...

We have performed all-electron ab initio calculations for TiB2 in the athermal limit using CRYSTAL95 code. The lattice parameters of AlB2-type structure were optimized as a function pressure. fitting Murnaghan equation state resulted values B0 = 292±1 GPa and B0' 3.34±0.03 bulk modulus its first derivative at zero linear along a-axis c-axis are Ba0 1031±3 (Ba0' 10.6±0.2) Bc0 675±3 (Bc0' 8.8±0.2), respectively. All five independent elastic constants calculated, analysis behaviour titanium...

We have investigated the structural changes induced by high-pressure in lithium disilicate glass with stoichiometric composition Li2O.2SiO2 (LS2). Using toroidal type chambers, samples were processed at 2.5 GPa, 4 6 GPa and 7.7 room temperature. Synchrotron X-ray diffraction measurements used to obtain radial distribution functions (RDF) order follow after processing high pressure. Compared a pristine sample, main change observed for up was associated distortion of SiO4 tetrahedral...

Abstract The main models proposed in the literature to describe pressure‐induced amorphization (PIA) are briefly reviewed, with special emphasis on kinetic aspects of PIA. high potential Raman spectroscopy for experimental studies PIA is highlighted and illustrated by results obtained zirconium tungstate (ZrW 2 O 8 ) boric acid (H 3 BO ). Compared x‐ray diffraction using a conventional tube, allowed much faster identification transitions both compounds. Further, ZrW have given support an...

The Knoop hardness of the highly incompressible cubic phase ruthenium dioxide was found to be 19–20 GPa from indentation tests. This value scales well with shear modulus approximated by elastic constant C44 144 obtained Brillouin scattering measurements. work provides evidence that is a better indicator than bulk for ionic and covalent materials.

Microporous AlPO4-54·xH2O, which exhibits the largest pores among zeolites and aluminophosphates with a diameter of 12.7 Å, was investigated at high pressure by X-ray powder diffraction Raman spectroscopy in diamond anvil cells. The material found to begin amorphize near 2 GPa using either nonpenetrating transmitting medium (PTM) silicone oil or no PTM. When H2O is used as PTM, amorphization begins lower 0.9 GPa. In this case, superhydration effects are observed higher relative unit cell...

The high-pressure behavior of the Prussian Blue analogue $\mathrm{Fe}[\mathrm{Co}{(\mathrm{C}\mathrm{N})}_{6}]$ has been explored by energy- and angle-dispersive x-ray diffraction, Fourier transform infrared, Raman spectroscopy. This cyanide-bridged framework material becomes amorphous above $10\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ form is retained upon pressure release. Samples recovered from around $17\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ exhibit a dark, metallic luster their spectra...

The pressure behaviour of a series transition metal borides has been studied both experimentally and by means ab initio calculations. X-ray diffraction patterns measured up to ∼50 GPa for VB2 ZrB2 show no obvious phase transition. Bulk moduli 322 317 GPa, respectively, were obtained using Murnaghan equation state. Hartree–Fock LCCO (linear combination crystal orbitals) calculations performed TiB2 have allowed its compression be studied. bulk modulus (292 GPa) the proposed important...

The aim of this work was to investigate the effect previous treatments at high pressures on crystallization kinetics monolithic samples a Li2O–2SiO2 (LS2) glass. glass transition temperature (Tg) and onset (Tp) obtained by differential thermal analyses (DTA) were measured for LS2 submitted isostatic ranging from 2.5 7.7 GPa during 5 min room temperature. observed systematic changes in Tg Tp probably related cracks induced pressure inside its surface. Away cracks, nucleation density slightly...

Niobium dioxide was studied up to 47 GPa by angle-dispersive, x-ray powder diffraction. Semiconducting $\ensuremath{\alpha}\ensuremath{-}{\mathrm{NbO}}_{2}$ (space group ${I4}_{1}/a,$ $Z=32)$ found transform $\ensuremath{\beta}\ensuremath{-}{\mathrm{NbO}}_{2}$ ${I4}_{1},$ $Z=16)$ above 5 GPa. Both phases have distorted rutile-type structures and the transition involves a change in long-range ordering of metal-metal bonds. A further observed 8 baddeleyite-related structure with $a=9.975(1),$...

A combined synchrotron X-ray diffraction, Raman scattering, and infrared spectroscopy study of the pressure-induced changes in H3BO3 to 10 GPa revealed a new high-pressure phase transition between 1 2 followed by chemical decomposition into cubic HBO2, ice-VI, ice- VII at ∼2GPa. The layered triclinic structure exhibits highly anisotropic compression with maximum along c direction, accompanied strong reduction interlayer spacing. large volume variation structural accompanying suggest high...

A nanostructured Ti50Ni25Fe25 phase (B2) was formed by mechanical alloying and its structural stability studied as a function of pressure. The changes were followed X-ray diffraction. B2 observed up to 7 GPa; for larger pressures, the transformed into trigonal/hexagonal (B19) that highest pressure used (18 GPa). Besides B19, elemental Ni or SS-(Fe,Ni) FeNi3 observed. With decompression, recovered. Using in situ angle-dispersive diffraction patterns, single line method applied obtain apparent...