Influence of sintering temperature on densification, microstructure, dielectric and ferroelectric properties of Li/Sb Co-doped KNN pizoceramics

Abstract

In this research, Li/Sb Co-Doped KNN ferroelectric powders have been successfully prepared and sintered at various temperatures. The effect of sintering temperature on microstructure and ferroelectric properties of this ceramic was investigated. The results indicate that pure KNN-LS piezoceramic synthesized without formation of conventional tungsten bronze phase. After sintering, a broad trident peak (2θ about 45–47°) in XRD pattern was completely observed which can be a substantial evidence for polymorphic phase transition (PPT) at room temperature. In the FESEM images, for all sintering temperatures, the bimodal cube-like morphology of KNN-LS particles remarkably appeared. The values of relative density increase from about 91% to 93%, with increasing temperature from 1115 to 1120 °C. Further increment in temperature up to 1150 °C causes a serious reduction of relative density (~86%). From 1115 to 1120 °C, relative permittivity (εr) increases due to about 2% increase in relative density then rapidly diminished when temperature reaches to 1150 °C. The maximum ferroelectric properties of Li/Sb Co-Doped KNN ceramic sintered at 1120 °C (the values of 17 and 14 μC/cm2 for the polarization saturation (PS) and polarization remanent (Pr), respectively) can be due to minimum pore volume of this ceramic during sintering process.