Impedance spectroscopy analysis of the diffuse phase transition in lead-free (Ba0,85Ca0,15)(Zr0.1Ti0.9)O3 ceramic elaborated by sol-gel method

Abstract

We investigate the lead free ferroelectric perovskite ceramic, (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT), prepared by sol-gel method. The as-synthesized precursor powder is calcined at 1000 °C for 4 h in order to obtain single-phase perovskite structure. X-ray diffraction (XRD) analysis at room temperature shows the formation of single-phase compound with a tetragonal structure refined in P4mm space group. The dielectric measurements in a frequency range of [100 Hz-1 MHz] and in a temperature range [35–400 °C] in the ceramic sintered at 1350 °C for 2 h, reveal a high maximum dielectric constant ∼5200 (100 Hz) at 107 °C, which is associated with ferroelectric paraelectric phase transition. The sol-gel method has displayed a very important advantages comparing to the conventional solid-state method. Special emphasis was done to characterize diffuse phase transition (DPT) that occurs close to ∼107 °C. We have shown that the real part of the permittivity close to DPT is well described by Santos–Eiras phenomenological model. Impedance spectroscopy analysis over the frequency range of 100 Hz to 1 MHz illustrated mainly bulk contribution up to 300 °C while grain and grain-boundary effects were present above 300 °C using the impedance spectroscopy technique.