Dielectric spectroscopy and magnetometry investigation of Gd-doped strontium titanate ceramics

Abstract

Structural, dielectric and magnetic properties of dense Gd-doped strontium titanate ceramics prepared by the conventional mixed oxide method are studied. Lattice parameter is found to decrease linearly in the Sr1-1.5xGd xTiO3 system, confirming the incorporation of Gd onto the Sr site of the perovskite lattice of strontium titanate up to x=0.05. Real and imaginary parts of the dielectric permittivity of Sr1-1.5xGd xTiO3 ceramics exhibit a relaxation between 100Hz and 1MHz in the temperature range of 17–26K, slightly shifting to higher temperatures with increasing Gd content. Such dielectric behaviour is attributed to the relaxation of individual dipoles formed by off-centre displacement of Gd3+ ions on Sr sites in a highly polarizable lattice of strontium titanate. Other dielectric relaxations observed in Sr1-1.5xGd xTiO3 from 125 to 300K are attributed to the oxygen vacancy related mechanisms. No magnetic anomaly but paramagnetic behaviour is observed for Sr1-1.5xGd xTiO3 ceramics, indicating an absence of the magnetic order and hence magnetoelectric coupling.