Thermal properties of lead germanate single crystals grown by the vertical Bridgman method

Abstract

Lead germanate single crystals (Pb 5Ge 3O 11:PGO) have been grown by the vertical Bridgman method. The dielectric measurements show that the Curie temperature of the PGO crystal is 447 K and the dielectric constant at room temperature is about 30. Thermal properties including specific heat, thermal diffusivity, thermal conductivity and thermal expansion have been investigated as a function of temperature for the first time. The specific heat of the PGO crystals has been measured to be 0.327 J/(g K) at 298 K. The thermal diffusivity and the thermal conductivity for PGO crystals are about 0.323 mm 2/s and 0.763 W/(m K) at 298 K, respectively. The average thermal expansion coefficients along the a- and c-directions of PGO crystals, calculated from 323–447 K, are 8.68×10 −6 and 6.60×10 −6 /K; however, it changes to 10.55×10 −6 and 6.07×10 −6 /K between 448–573 K, respectively.