Single crystals were grown by the reverse temperature gradient method from phosphoric acid solutions under hydrothermal conditions. Twins after (110) were studied by etching faces having been cut perpendicular to one of the twofold axes. Based on the determination of the twin boundary position as well as on the knowledge of the growth rates of different crystallographic forms, a few faces were chosen to be quite promising for growing high-quality GaPO4 single crystals if they were offered at the referring seed crystal. From the characterization of the grown crystals conditions were found, which may lead to the reduction of the inversion twin number during the growth process.

Reducing Inversion Twinning in Single Crystal Growth of GaPO4. M.Grassl, R.U.Barz, P.Gille: Crystal Research and Technology, 2002, 37, 531