Normal-relaxor ferroelectric phase transition induced morphotropic phase boundary accompanied by enhanced piezoelectric and electrostrain properties in strontium modulated Bi0.5K0.5TiO3 lead-free ceramics

摘要

In this work, (Bi0.5K0.5)(1-x)SrxTiO3 compositions (x = 0.03 similar to 0.18) are designed to clarify the role of normal-relaxor ferroelectric phase transition and morphotropic phase boundary on dielectric, piezoelectric and electrostrain properties. With increasing strontium content, tetragonal distortion decreases and tetragonal and pseudocubic phases coexist in 0.09 <= x <= 0.15 compositions; the spontaneous phase-transition temperature and curie temperature decrease, as certified by phase-structure, dielectric properties and Raman spectra analysis. Optimized piezoelectric constant similar to 106 pC/N and electrostrain similar to 0.17 % are obtained for (Bi0.5K0.5)(0.88)Sr0.12TiO3 composition. Piezoelectric force microscopic technique is exploited to clarify the origin of enhancement in macroscopic performances. Increase in temperature enhances ferroelectric performance and a large strain value similar to 0.25 % with low hysteresis similar to 27 % are obtained at 140 degrees C for the optimized composition, which are believed to originate from electric-field induced relaxor-to-ferroelectric phase transition with thermally-activated reduced energy barriers. This work clearly demonstrates that lead-free Bi0.5K0.5TiO3-based ceramics are another promising bismuth-based species in applications of piezoelectric sensors and actuators.