LAUSR

ABSTRACT Single crystals of Pb5Ge3O11 (PGO), pure and doped with Cr3+ ions, were grown by means of Czochralski and Kyropoulos method, respectively. Structural, microstructural, thermodynamic and dielectric properties were investigated in terms of Cr3+-doping. The temperature dependences of molar heat capacity in the range 120–700 K at constant pressure (cp) for PGO and PGO:Cr3+ (0.2%) crystals were shown. Wide λ-shape anomalies correspond to the second-order phase transitions from ferroelectric to the paraelectric phase taking place at 453 K and 431 K for PGO and PGO:Cr3+ (0.2%), respectively. The temperature dependences of cp for investigated crystals were approximated by the Einstein function and near the Curie temperature the cp reaches the classical Dulong-Petit limited value ∼475 J·mol−1·K−1. Temperature dependences of dielectric permittivity measured along and perpendicular to the ferroelectric axis in the temperature range 300–550 K are investigated. These studies revealed anisotropic behavior of PGO and PGO:Cr3+ (0.2%) crystals.