Dielectric and Impedance Analysis on the Electrical Response of Lead-Free Ba1-xCaxTi0.9Zr0.1O3 Ceramics at High Temperature Range

Ba1-xCaxTi0.9Zr0.1O3 (x = 0.10, 0.15, 0.18) solid solutions were synthesized by the conventional solid-state method. A perovskite-type structure was determined using the X-ray diffraction (XRD) technique. The addition of Ca2+ reduced the grain size (22.6, 17.9 and 13.3 m, respectively) for all well-sintered ceramics (approximate to 98%). Moreover, the stability temperature ranges for the tetragonal phase were promoted by displacing the ferroelectric-ferroelectric phase's transition temperatures while T-C was maintained (86 degrees C). The electrical performance of the material improved as the stoichiometric composition was positioned near the morphotropic phase boundary (x = 0.15): epsilon(r) approximate to 16,500 (T-C) at 1 kHz. For T > T-C, a thermally activated relaxation process occurred. In addition, the bulk and grain boundary processes were responsible for the conduction mechanisms. The composition x = 0.15 showed an activation energy of Ea = 1.49 eV with a maximum conductivity of sigma(max) = 2.48 x 10(-2) Sm-1 at 580 degrees C. Systematic studies at high temperature for dielectric properties were accomplished for analyzing electrical inhomogeneities associated with the grain, grain boundaries or surfaces, which are important for device design and a fundamental electrical characterization.