A new polymorph of GaAsO4

Abstract

At room temperature, the compound GaAsO 4 (gallium arsenate) has a berlinite type structure (AlPO 4, P3 121) and it is the only normal pressure polymorph reported as occurring at all temperatures. By means of a gaseous phase route, GaAsO 4 was obtained in a structure homeotypic with α-cristobalite and was retained at room temperature. Structural Rietveld refinement of this new GaAsO 4 polymorph was performed based on space group C222 1 and refined lattice parameters are a = 7.0592 Å, b = 7.0893 Å, c = 7.0977 Å. Heating up to 1000°C the α-cristobalite homeotype transforms to the stable berlinite type structure and it would invert to the β-cristobalite homeotype at about 530°C.