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V2O5 phase diagram revisited at high pressures and high temperatures

“…The HP-HT runs with in situ XRD measurements performed at the Photon Factory (Tsukuba, Japan) revealed the presence of two new HP-HT phases at 4.9 GPa and 350 • C, and at 10.1 GPa and 400 • C, respectively. By comparing the XRD patterns obtained by Kusaba et al [15] with the ones previously reported by Suzuki et al [10], Volkov et al [11] and Filonenko and Zibrov [14], it is evident that the two HP phases found by Kusaba et al [15] correspond to the ␤-and B-phases, respectively. In addition to their in situ runs, Kusaba et al [15] performed quench experiments in large volume devices (using a different HP-HT press), to pressures up to 10 GPa and temperatures up to 500 • C. The structure obtained at 6 GPa and 500 • C was identical to the one from the in situ run performed at 4.9 GPa and 350 • C. Further quench experiments at pressures up to 10 GPa resulted in a mixture of the two HP-HT modifications observed in the in situ work, but no pure B-phase was obtained up to 10 GPa.…”

“…Filonenko and Zibrov [14] performed quench experiments in a large volume press (toroidal device), up to 8.5 GPa and up to 1100 • C. In this P-T region the authors [14] found the ␤-phase up to 7.5 GPa and 900 • C and a new phase, which they have labelled B-V 2 O 5 , at 8-8.5 GPa and from 600 to 1100 • C. The authors identified this B-phase as being isostructural with Sb 2 O 5 [16] and with the B-forms of Nb 2 O 5 and Ta 2 O 5 , but with smaller lattice parameters. The return from both B-and ␤-phases into the ␣-phase at atmospheric pressure seems to be associated with strong exothermal behaviour at ≈250 and 400 • C, respectively [14].…”

“…In both publications, by Filonenko and Zibrov [14] and Kusaba et al [15], the ␤-phase was described as orthorhombic with almost identical lattice parameters. However, in a more recent study, Filonenko et al [17] re-analyzed the ␤-phase of V 2 O 5 obtained post HP-HT experiments, using XRD, neutron powder diffraction, and high-resolution transmission electron microscopy (HR-TEM), and found the structure to be monoclinic.…”

“…In 2001 two different groups [14,15] published their findings on the V 2 O 5 phases investigated at elevated pressures and temperatures. Filonenko and Zibrov [14] performed quench experiments in a large volume press (toroidal device), up to 8.5 GPa and up to 1100 • C. In this P-T region the authors [14] found the ␤-phase up to 7.5 GPa and 900 • C and a new phase, which they have labelled B-V 2 O 5 , at 8-8.5 GPa and from 600 to 1100 • C. The authors identified this B-phase as being isostructural with Sb 2 O 5 [16] and with the B-forms of Nb 2 O 5 and Ta 2 O 5 , but with smaller lattice parameters.…”

SiC-Based Composites Sintered with High Pressure Method

“…Sintering process in a Bridgman-type HPHT system. Quasi-hydrostatic compression of the preliminary consolidated powders (sample -1) is achieved as a result of plastic deformation of the gasket material (2) between anvils (3); electrical heating is provided by a high-power transformer (4) and graphite resistive heater (5) Gaskets are made of special kinds of metamorphic rocks such as pyrophyllite, "lithographic stone" or catlinite (Filonenko & Zibrov, 2001;Prikhna, 2008). The toroidal chamber, depending on its volume (usually from od 0.3 do 1 cm 3 ), can generate pressures up to 12 GPa and temperature up to ~2500 °C.…”