Temperature-Dependent Tunability in the Paraelectric State of BaTiO3-Based Solid Solutions

The electric field dependence of the dielectric constant (dc-tunability) as a function of composition at a few temperatures was investigated for BaTiO3-based solid solutions. Dense and homogeneous BaZrxTi1-xO3 ceramics (ferroelectric: x = 0.10 and x = 0.15 and relaxor: x = 0.18) with high dielectric constant and low losses were prepared by solid state reaction and their dc-tunability characteristics were investigate at a few temperatures from 20 to 70 degrees C, including the Curie range. The nonlinear epsilon(E) dependences were described using the Johnson's approach plus an additional term. A model of random uncorrelated non-interacting dipolar units in a double well potential was employed for the epsilon(E) in the paraelectric state of the composition x = 0.18. For this composition, the average dipole moment of the nanopolar regions as a function of temperature was determined.