Growth zones and their boundaries in GaPO4

Gallium (ortho)-phosphate (GaPO4) is a piezoelectric material which is grown from hydrothermal solutions. The growth zones, i.e. parts of the crystal grown by different faces, and their boundaries can influence the quality of the grown material. Thus, a theoretical and experimental study of form, size and properties of growth zones and their boundaries in GaPO4 was performed. A program was developed with which the zones in the crystal as well as in any plane cutting through it can be calculated and outlined, simulating the facetted growth using growth rates determined from the crystal habit. This program was applied to spontaneous crystals as well as to crystals growm from seeds. Experimentally, growth zone boundaries which correspond to accumulation of OH were determined by scanning infrared absorption measurements.