Crystal structures of α-quartz homeotypes boron phosphate and boron arsenate: structure-property relationships

Abstract

Abstract The structures of single crystals of the α-quartz homeotypes boron phosphate and boron arsenate prepared under high-pressure, high-temperature conditions in a belt-type apparatus were determined by X-ray diffraction. Both structures are more distorted with respect to the β-quartz structure type than α-quartz itself with average tetrahedral tilt angles δ of 19.7° and 24.6° for BPO4 and BAsO4, respectively. The structure of BAsO4 is one of the most highly distorted found among α-quartz homeotypes. It is shown that for the known α-quartz homeotypes, the density, which can be related to the frequency constant for piezoelectric resonators, scales with the intertetrahedral bridging angle θ.