Growth and characterization of large size lead germanate single crystals

Ferroelectric lead germanate crystal (Pb5Ge3O11, PGO) has been grown by the vertical Bridgman method. Compositional deviation and cracking were the main problems often encountered during the growth. The polycrystalline PGO powder was pre-synthesized by sintering the PbO and GeO2 mixture with slight GeO2 excess. An in situ annealing process was employed to prevent PGO crystals from cracking during cooling. PGO single crystals up to 55 mm in diameter and 35 mm in length were obtained. Dielectric properties of the grown PGO crystal were measured.