Dielectric relaxation study of solid solution of lead magnesium niobate and La-doped bismuth titanate

The diffuse phase transition characteristic of PMN is now believed due to the distribution of ordered and disordered phases on microscopic scales, which can coexist over a broad temperature interval. In this investigation La-doped BT is mixed with PMN to reduce the coupling between polar microregions. Phase analysis exhibits the phase transition of BLT from orthorhombic to cubic phase with lattice parameter similar to 20.68 angstrom. Electric field induced polarization demonstrates the decrease in the saturation polarization and small increase in the remanent polarization. Temperature dependence of dielectric constant reveals the presence of relaxor-like permittivity behaviour in 50-120 degrees C temperature range. BLT addition in PMN led into decrease in the dielectric constant from 20,000 (100 Hz) to 800 (100 Hz). The difference in the temperature of epsilon(max) between 100 Hz and 100 KHz frequencies was found to increase, which is due to increase in the degree of relaxation.