Elastic characterizations of α-GaPO4 single crystals grown by the flux method

Abstract

Transparent gallium orthophosphate single crystals with theα-quartz-typestructure, α-GaPO4, were obtained using the high temperature solution growth technique in aLi2O–3MoO3 flux. A first measurement of several elastic constantsCijkl of themillimeter-size α-GaPO4 piezoelectric single crystals obtained is reported. The elastic constants were computed fromthe resonance frequencies of the thickness vibration modes measured, at room temperature,in plates polished in these crystals. These resonances were excited either by an electric fieldnormal to the plates (conventional thickness excitation) or by a field parallel tothe surface of the plates (lateral field excitation). As usual, the elastic constantswere extracted using the formulae given by the corresponding one-dimensionaltheories of thickness vibration of piezoelectric plates. The measured elastic constantsCijkl of theflux-grown α-GaPO4 were generally found to be higher than those measured withα-GaPO4 crystals grown using the hydrothermal technique. This is most probably related to theextremely weak concentration of OH impurities existing in the crystals obtained using thisflux-growth method.