High-pressure X-ray diffraction study of SrMoO4 and pressure-induced structural changes

Abstract

SrMoO 4 was studied under compression up to 25 GPa by angle-dispersive xray diffraction. A phase transition was observed from the scheelite-structured ambient phase to a monoclinic fergusonite phase at 12.2(9) GPa with cell parameters a = 5.265 (9) Å, b = 11.191(9) Å, c = 5.195 (5) Å, and β = 90.9°, Z = 4 at 13.1 GPa. There is no significant volume collapse at the phase transition. No additional phase transitions were observed and on release of pressure the initial phase is recovered, implying that the observed structural modifications are reversible. The reported transition appeared to be a ferroelastic second-order transformation producing a structure that is a monoclinic distortion of the low-pressure phase and was previously observed in compounds isostructural to SrMoO 4 . A possible mechanism for the transition is proposed and its character is discussed in terms of the present data and the Landau theory. Finally, the EOS is reported and the anisotropic compressibility of the studied crystal is discussed in terms of the compression of the Sr-O and Mo-O bonds.

Pressure-induced phase transitions in AgClO4

“…The high-temperature F43m phase 41 has an AgCl-subarray of the zincblende type and is consistent with the stabilization of the cubic phase upon heating, as it was reported for many other compounds. 15,16 This feature, in turn, agrees with the concept that relates oxidation and pressure, 42 which will be discussed below. Following this concept, compression induces a volume and symmetry reduction in AgClO 4 , but heating of the oxide releases pressure, producing a reversion of the structural changes.…”

“…11) and with several high-pressure transitions detected in scheelites and related oxides. [12][13][14][15][16][17][18] In contrast with zircon, scheelite, and anhydrite, the effects of pressure on the crystal structure of silver perchlorate have not been studied yet. Here, in order to improve the understanding the high-pressure behavior of ABO 4 oxides, we report a combined experimental and theoretical study of AgClO 4 .…”

High-pressure stability and compressibility ofAPO4(A=La, Nd, Eu, Gd, Er, and Y) orthophosphates: An x-ray diffraction study using synchrotron r

“…Tb and Y) the zircon-monazite transition should be induced by pressure, as we found in YPO 4 and ErPO 4 . Given there is an inverse relationship between pressure and temperature in ABO 4 compounds [26], this explanation is in full agreement with the fact that monazite is the low-temperature form of TbPO 4 and zircon is the hightemperature form of GdPO 4 [27].…”

Experimental and theoretical investigation ofThGeO4at high pressure

“…26͒ and SrMoO 4 . 5 When compressing the scheelite-structured sample, we found no phase transition from ambient pressure up to 24.4 GPa. Beyond this pressure we found the broadening of diffraction peaks in addition to the appearance of new reflections.…”

“…3 In particular, high-pressure ͑HP͒ studies have been performed on them in order to understand their mechanical properties and HP structural behavior. [3][4][5][6][7][8][9][10] Among these studies the majority focus on zircon-type silicates, e.g., ZrSiO 4 ͑Refs. 8-10͒ and scheelite-type tungstates, e.g., CaWO 4 .…”