Growth defects of lead germanate single crystals grown by the vertical Bridgman method

Lead germanate, Pb5Ge3O11 (PGO) single crystals have been grown by the modified vertical Bridgman method. An optical microscope and an electron probe X-ray microanalyser (EPMA) were used to investigate the growth defects, such as inclusions, negative crystal, bubbles and boundaries. Light scattering particles were observed, most of which were related to PbO inclusions. The formation of negative hexagonal crystals is described. Bubbles and boundaries were also observed in as-grown PGO crystals. An incomplete cleavage plane was also found. To reduce and eliminate growth defects, some suggestions are presented which were performed during growth experiments.