Segregation forming and growth defect characterization by heat treatment of hydrothermally grown GaPO4

Abstract Quartz-type gallium (ortho-)phosphate (GaPO 4 ) is grown hydrothermally from acid solutions. By heating to 600–800°C for several hours, defects containing OH groups segregate in submicroscopic bubbles which form various patterns relating to growth defects. The formation of oriented disks and star-like forms, as well as of helices, is attributed to passive climbing of step dislocation loops, sometimes originating at local growth defects. Growth dislocations are decorated and show effects of dislocation climbing. Boundaries between growth zones and Brazil twin boundaries become clearly visible. Bands and growth striations are attributed partly to growth condition fluctuations, partly to macrostep propagation. The microscopic investigation of patterns created by heat treatment thus has been shown to be a convenient method for characterization and the study of growth defects and offers insight into segregation formation and dislocation dynamics of GaPO 4 .