New approach of crystal growth and characterization of a quartz and berlinite isomorph: GaPO4

GaPO₄ crystal growth in sulfuric and phosphoric acid media through the slow heating and vertical reverse temperature gradient methods is discussed. The systematic study of growth parameters shows a V_χ growth rate always much greater than V _z and V_y. It is possible to epitaxially grow GaPO₄ on large berlinite seeds in sulfuric acid and to use them for GaPO₄ crystal growth in phosphoric acid. The epitaxial process and crystalline quality are analyzed by X-ray topography. Infrared spectrometry proves a lower OH concentration than in the berlinite case for approximately the same crystal growth conditions. First piezoelectric characterizations for resonators near the AT-cut show GaPO₄ to be a very promising piezoelectric material with a large coupling coefficient near 16%, a quartzlike thermal stability, and a Q factor nearly sufficient for the applications