0000000000364988
AUTHOR
Jean Ravez
High frequency dielectric relaxation in BaTio3derived materials
Abstract A systematic study of the dielectric relaxation phenomenon has been carried out for ceramics with compositions derived from barium titanate in the frequency and temperature ranges 1 MHz–1 GHz and 250–500 K, respectively. Whatever the composition may be, a minimum of the relaxation frequency and a maximum of the dielectric dispersion appears at each phase transition temperature. The dipole-type relaxation is correlated to coherent displacements of the ions in the octahedron sites ordered either along chains or in 3D-lattice.
Dielectric relaxation in crystals and ceramics derived from BaTiO3
Abstract A dielectric relaxation is reported in a crystal of BaTiO3 and in ceramics with composition (Ba1-yCay)TiO3 (0≤y≤0.2) in the frequency and temperature ranges 106 to 109 Hz and 350 to 450 K, respectively. A minimum of the relaxation frequency occurs close to the ferroelectric Curie temperature. The relaxation is of dipolar-type.
Relaxor ferroelectric ceramics of LiTaO3-type
Abstract A ferroelectric relaxation has been identified in Li1-xCax (Ta1-xZrx)O3(x = 0.15 and 0.20) ceramics with LiTaO3-type structure. The relaxation frequency fr is minimum and the dispersion step (ϵ′S - ϵ′∞) is maximum at TC. When x increases, a higher conductivity associated with a lower activation energy and a decrease of the magnitude of fr at Tc are observed, while the unit cell volume becomes larger, TC lower and the transition more diffuse.