A quartz-like material: gallium phosphate (GaPO 4); crystal growth and characterization

Abstract

This investigation concerns GaPO 4 crystal growth in sulphuric and phosphoric acid media through the slow heating and vertical reverse temperature gradient methods. Systematic study of growth parameters shows that the growth rate V x is always much greater than the two other ones, V z and V y . The most interesting result is the ability to produce GaPO 4 epitaxy on large berlinite seeds in sulphuric acid and to use them for GaPO 4 crystal growth in phosphoric acid. The epitaxial fit and the crystalline quality have been checked by X-ray topography. The [OH] content, determined by infrared spectrometry, seems to prove a lower OH concentration than in case of berlinite when approximatively the same crystal growth conditions are used. First piezoelectric characterizations for resonators near the AT cut show GaPO 4 to be a very promising piezoelectric material with a large coupling coefficient near 16%, a quartz-like thermal stability and a Q factor already nearly sufficient for the applications.