Effect of Zr substitution on electrical properties of Ba0.90Sr0.10Ti1_ xZrxO3 (0 <= x <= 0.20) ceramics

Abstract

In this article, the effect of Zr addition on the crystalline structure, ferroelectric and piezoelectric properties of Barium Strontium Titanate (BST) ceramic have been studied. Zr was doped in the range of 0 <= x <= 0.20 in Ba0.90Sr0.10Ti1-xZrxO3 (BSZT) and it was prepared via solid state reaction technique. From the characterization studies, it was realized that Zr addition in BSZT ceramics results in slight modification of BSZT lattice, but due to diffusion of Zr into the lattice, the crystallite size as well as the microstructure of combined BSZT system got modified drastically. Zr addition in BSZT ceramics results in increase of lattice parameter due to larger ionic radius of Zr ions compared to Ti ions. Reduction of grain and crystallite size was also observed, which affects the ferroelectric behaviour of BSZT ceramic by influencing the polarization contribution from individual domains. This causes a slow transformation of sharp paraelectric-ferroelectric transition to diffusive ferroelectric phase transition and it also introduces relaxation phenomenon in the system at higher Zr compostion, which convert it to a relaxor ferroelectric. At relaxor phase a decreased spontaneous polarization and slimmer P-E hysteresis loop was observed with increasing Zr content. The main reason behind this conversion and modification in micro -structural properties is because of the presence of strain in BSZT lattice which is due to replacement of Zr4+ (0.72 angstrom) inplace of smaller Ti4+ (0.609 angstrom) in more than a tolerable limit. Substitution of Zr4+ for Ti4+ in BaSrTiO3 introduces structural disorder, causing perturbations like local electric and strain fields. These perturbations reduce the long-range polar order resulting in relaxor behavior.