Dielectric and tunability properties of La-doped BaTiO3 ceramics

La-doped BaTiO3 (x = 0.001; 0.0025; 0.005; 0.01; 0.025) ceramics were prepared via conventional solid state reaction and sintered at 1300 degrees C for 6 h, resulting in dense single phase ceramics with homogeneous microstructures. The temperature dependence of dielectric permittivity of the ceramics has been investigated. The results show a decrease of T-C with lanthanum addition. The degree of diffuseness of phase transition is more pronounced for high La content, implying the existence of a composition-induced phase transition of the ceramics. The dc-tunability at room temperature was investigated and experimental data were discussed in terms of the Johnson model completed with a Langevin term that describes "extrinsic" contribution to the non-linear epsilon(E) dependences. (C) 2011 Elsevier B.V. All rights reserved.