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

Abstract

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 μm, respectively) for all well-sintered ceramics (≈98%). Moreover, the stability temperature ranges for the tetragonal phase were promoted by displacing the ferroelectric-ferroelectric phase’s transition temperatures while TC was maintained (86 °C). The electrical performance of the material improved as the stoichiometric composition was positioned near the morphotropic phase boundary (x = 0.15): εr ≈ 16,500 (TC) at 1 kHz. For T > TC, 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 σmax = 2.48 × 10−2 S·cm−1 at 580 °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.

Keywords

• BCTZ ceramics
• dielectric response
• impedance spectroscopy