Neutron and X-Ray Structure Refinements between 15 and 1073 K of Piezoelectric Gallium Arsenate, GaAsO4: Temperature and Pressure Behavior Compared with Other α-Quartz Materials

Previous X-ray crystal structure refinement of GaAsO4 gave spurious As–O (1.72 A) and Ga–O (1.77 A) bond distances by comparison with theoretical values and with experimental values from AlAsO4 and GaPO4 ([As–O]≅1.67 A and [Ga–O]≅1.82 A). Therefore, a complete structural reinvestigation of gallium arsenate was carried out between 15 and 1073 K by both neutron and X-ray diffraction. All new analyses led to experimental bond values in agreement with those predicted, i.e., close to 1.67 and 1.82 A. This new structural investigation of GaAsO4 over a wide range of temperatures emphasizes the high thermal stability of the α-quartz packing in this compound, the best amongst quartz-like materials. The experimental relation between structural deformation and piezoelectric properties of these quartz-like materials also allows us to predict that GaAsO4 would have the best piezoelectric characteristics for its AT-cut. Conversely, its higher covalent character should imply a greater pressure sensitivity, with a crystal structure transition around 9 GPa. Thus, GaAsO4 would be the best piezoelectric candidate for high temperature applications but not for high pressure devices.