X-ray and dielectric studies of ferroelectric or relaxor phases in the Ca1−xNaxSn1−xNbxO3 system

Ceramics with composition Ca1−xNaxSn1−xNbxO3 (0.85⩽x⩽0.96) were sintered in the temperature range 1200-1400 °C. Dielectric properties of ceramics belonging to the whole composition domain were investigated in a broad range of temperatures (80-600 K) and frequencies (0.1-200 kHz). The thermal behavior of the dielectric permittivity suggests the existence of three phases: cubic-paraelectric, tetragonal-paraelectric and orthorhombic-ferroelectric or relaxor. The relaxor, or classical ferroelectric character, is dependent on the value of x. The symmetries of these three phases were investigated by X-ray diffraction study. The polarization state was checked by piezoelectric and pyroelectric measurements.