Investigation of phase structure, microstructure, and electrical properties of LaAlO 3 -modified alkali niobate lead-free perovskite

LaAlO3 as an effective additive for modification of KNN system has never been systemically discussed before. Here, (0.96−x)K0.48Na0.52NbO3–0.04Bi0.5Na0.5ZrO3–xLaAlO3 (KNN–BNZ–xLA) ceramics have been synthesized by traditional solid-state sintering with a special emphasis on the influences of LaAlO3 components on the crystallographic structure, microstructure, and electrical properties. XRD and Rietveld refinements were performed to explore the effects of LaAlO3 on the phase evolution and the crystallographic structure, respectively, which revealed a coexistence of tetragonal and orthogonal phases. And through the results of the temperature-dependent dielectric constant (e r−T), we found the phase boundary shifted to low temperature slowly with the increase of LaAlO3 components. As a resut, the samples with x = 0.004 demomstrated the excellent properties of d 33 ~ 354 pC/N, k p ~ 46%, T C ~ 325 °C, P r ~ 21.8 μC/cm2, tan δ ~ 3.9%, together with a high strain value as high as 0.18% at 50 kV cm−1, which are originated to the contributions of the crystallographic structure transition and dense microstructure. Additionally, it is worth noting that such a good thermal stability of piezoelectricity (e.g., d 33 ≥ 303 pC/N, T ≤ 300 °C) was also observed by thermal depoling method and temperature-dependent P–E hysteresis loops. Not only is this work itself scientifically fascinating but it also renders these materials appealing for practical applications as a candidate for lead-based ones.