Neutron and X-ray structure refinements between 15 and 1073 K of piezoelectric gallium arsenate, GaAsO4: Temperature and pressure behavior compared with other alpha-quartz materials

Previous X-ray crystal structure refinement of GaAsO4 gave spurious As-O (1 .72 Angstrom) and Ga-O (1.77 Angstrom) bond distances by comparison with th eoretical values and with experimental values from AlAsO4 and GaPO4 ([As-O] congruent to 1.67 Angstrom and [Ga-O] congruent to 1.82 Angstrom). Therefo re, a complete structural reinvestigation of gallium arsenate was carried o ut between 15 and 1073 K by both neutron and X-ray diffraction. All new ana lyses 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 o ver a wide range of temperatures emphasizes the high thermal stability of t he alpha-quartz packing in this compound, the best amongst quartz-like mate rials. The experimental relation between structural deformation and piezoel ectric properties of these quartz-like materials also allows us to predict that GaAsO4 would have the best piezoelectric characteristics for its AT-cu t. Conversely, its higher covalent character should imply a greater pressur e sensitivity, with a crystal structure transition around 9 GPa. Thus, GaAs O4 mould be the best piezoelectric candidate for high temperature applicati ons but not far high pressure devices. (C) 1999 Academic Press.