An Investigation of the Pressure-Induced Structural Phase Transition of Nanocrystalline α-CuMoO4

Abstract

The structural behavior of nanocrystalline α-CuMoO4 was studied at ambient temperature up to 2 GPa using in situ synchrotron X-ray powder diffraction. We found that nanocrystalline α-CuMoO4 undergoes a structural phase transition into γ-CuMoO4 at 0.5 GPa. The structural sequence is analogous to the behavior of its bulk counterpart, but the transition pressure is doubled. A coexistence of both phases was observed till 1.2 GPa. The phase transition gives rise to a change in the copper coordination from square-pyramidal to octahedral coordination. The transition involves a volume reduction of 13% indicating a first-order nature of the phase transition. This transformation was observed to be irreversible in nature. The pressure dependence of the unit-cell parameters was obtained and is discussed, and the compressibility analyzed.

Exploring the crystal structure and properties of ytterbium orthoantimonate under high pressure

“…The high-pressure (HP) behaviour of MTO 4 bimetal oxides has been the focus of research interest during the last two decades. 1,2 The main objects of study have been phosphates, 3,4 vanadates, 5,6 tungstates, 7,8 molybdates, 9,10 chromates, 11,12 niobates, 13,14 and tantalates. 15,16 On the other hand, a group of compounds that have been barely studied under HP are orthoantimonates, among which only BiSbO 4 has been studied.…”

Revealing the local structure of CuMo$_{1-x}$W$_x$O$_4$ solid solutions by multi-edge X-ray absorption spectroscopy

“…In pure CuMoO 4 and at low tungsten content (x < 0.15), a first-order phase transition between α and γ phases takes place and is accompanied by a change in the coordination of molybdenum/tungsten atoms by oxygen atoms from tetrahedral to octahedral [4,5]. The phase transition can be induced by temperature or pressure and is accompanied by a color change, demonstrating thermochromic or piezochromic properties [2,4,5,6,7,8,9,10,11,12]. The high-temperature (low-pressure) phase is greenish, whereas the low-temperature (high-pressure) phase is brownish [4,5].…”