Structure and electrical properties of IrO2-doped 0.5Ba0.7Ca0.3TiO3–0.5BaTi0.8Zr0.2O3 ceramics via low-temperature sintering

Abstract

Lead-free ceramics 0.5Ba0.7Ca0.3TiO3–0.5BaTi0.8Zr0.2O3–xIrO2 (x = 0–1.2 %) were prepared at a low temperature of 1260 °C via sintering the as-synthesized nanoparticles, which were synthesized by a modified Pechini polymeric precursor method. All samples featured high levels of densification under the synthesis conditions; particularly, the ceramic prepared at IrO2 content of 0.4 % achieved the highest relative density (~97.4 %). Phase transition from tetragonal to orthorhombic and a polymorphic phase transition (PPT) region were observed, which were influenced by the IrO2 content. The dielectric properties, temperature coefficient of capacitance, ferroelectric properties, and piezoelectric properties as a function of IrO2 content were thoroughly studied. Optimal electrical properties (remnant polarization, piezoelectric constant, and planar electromechanical coupling factors, i.e., Pr = 6.28 μC/cm2, d33 = 199 pC/N, and kp = 0.258) were obtained around the PPT region. The findings of the ceramic electrical properties by IrO2 doping are believed to be insightful in the development of lead-free dielectric and ferroelectric materials.