Temperature stability and electrical properties of Tm₂O₃ doped KNN-based ceramics

For green development concern, lead-free piezoelectric ceramics 0.96(K_0.48Na_0.52)Nb_0.96Sb_0.04O₃–0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃–xmol%Tm₂O₃ fabricated via conventional solid state method are studied. The analyses of X-ray diffraction and Raman dates show the coexistence phase of orthorhombic–tetragonal. Meanwhile, the tetragonal fraction increases with increasing Tm contents. Both the Cure temperature and the responding maximum permittivity decline with increasing x. At the same time, there are diffuse phase transition and relaxation-like phenomena after doping Tm. The activation energy, obtained from Arrhenius equation, suggests that there is a mixed conduction mechanism by both single-ionized and doubly oxygen vacancy diffusion. The temperature stabilities of remnant polarization and unipolar strain are significantly improved in the temperature range of 30–150 °C. Rare earth element Tm is useful for improving the temperature stability of the KNN-based piezoelectric ceramics.