Effect of sintering temperature on the microstructural and electrical properties of non stoichiometric strontium bismuth tantalate ferroelectric ceramics

In recent times due to the increased environmental awareness, lead free bismuth layer structured ferroelectrics are being investigated as an alternative to the lead based ferroelectrics due to their high dielectric constant and remnant polarization. Strontium bismuth tantalate is one of the interesting lead free compounds being widely investigated. However, in these compounds it is difficult to maintain the stoichiometry as bismuth gets evaporated due to sintering at high temperature leaving behind the vacancies which affect the properties. In the present work, specimens with different strontium and bismuth content having compositions Sr_1−xBi_2+xTa₂O₉ (x = 0.0 and 0.2) were prepared. The preparation conditions have been optimized with an objective to get enhanced electrical properties. The structural characterizations have been done using X-ray diffraction and scanning electron microscopy. Dielectric studies as a function of temperature have been carried out. Dielectric constant is observed to be higher in non-stoichiometric composition and dielectric loss reduces significantly. A maximum 2Pr (∼16 μC/cm²) is obtained in composition with the x = 0.2 when sintered at 1,150 °C. The observed behavior has been explained in terms of the microstructural features and inherent lattice defects. The present study reveals an optimum sintering temperature of 1,150 °C for the enhanced structural and electrical properties. (author)