Grain and grain boundary contributions to AC conductivity in ferroelectric Ba0.75Pb0.25Ti1-xZrxO3 ceramics

Abstract

The structural, electrical, ferroelectric, and piezoelectric properties of Zr substituted Ba0.75Pb0.25Ti1-xZrxO3 perovskite series were investigated. The structural phase refinement of x-ray diffraction data revealed the coexistence of tetragonal and orthorhombic phases in the substituted samples. Raman studies also supported the mixed phases for the substituted samples. Tetragonality was found to reduce as the fraction of the orthorhombic phase increased with Zr doping. No morphotropic phase boundary was observed. The variation of AC conductivity had been discussed considering the possibility of oxygen vacancies in the grains and grain boundaries. Remnant polarization (Pr) and coercive field (Ec) were modified with the Zr concentration. All samples showed excellent energy storage properties. The piezoelectric charge coefficient (d33) improved with Zr incorporation. Incorporation of Pb in BaTiO3 increased the tetragonal to cubic phase transition temperature (Tc). However, additional Zr incorporation resulted in diffused transition with Tc getting reduced with the increasing Zr content. Consequently, the substituted materials exhibited a high dielectric constant and low loss above the room temperature. This makes these materials a promising candidate for various technological applications over a wide temperature range, above room temperature.