The high piezoelectricity and thermal stability of high-temperature piezoelectric ceramics BiFeO3-0.25BaTiO3-xBi0.5K0.5TiO3 near the MPB

Lead-free high-temperature piezoelectric ceramics of 1 mol% Mn-doped (0.75 - x)BiFeO3-0.25BaTiO(3)-xBi(0.5)K(0.5)TiO(3) were prepared via a conventional solid-state sintering technique. The relationship between the phase structure and the electrical properties of this system was disclosed. A composition-induced structural transformation from rhombohedral to tetragonal was induced by increasing the BKT concentration. A morphotropic phase boundary (MPB) was formed at x = 0.010-0.015, which was confirmed by the Rietveld refinement and Raman spectroscopy deconvolution. In particular, the ceramic with x = 0.010 exhibits excellent performances with d(33) = 149 pC N-1, k(p) = 38%, P-r = 28.2 mu C cm(-2) and T-C = 615 degrees C. The high-temperature piezoelectricity of the sample with the MPB (x = 0.010) was characterized by in situ Raman spectroscopy and in situ d(33) testing. The outstanding thermal stability of the crystal structure and the high depolarization temperature (T-d similar to 570 degrees C) indicate that the BF-BT-BKT system is a promising candidate for lead-free high-temperature piezoelectric sensing.