The evidence of samarium substitution defect contributing to local structural-polar heterogeneity and Tc in Sm-doped 0.68PMN-0.32PT ceramics compensated by B-site vacancies

Abstract

B-site vacancy is introduced by component design to provide an easy way to detect samarium substitution defects in Sm-doped 0.68PMN-0.32PT ceramics (The optimum d₃₃ = 1004 pC/N for x = 0.025). The thorough examination of defects through positron annihilation lifetime and coincidence Doppler broadening spectroscopy indicates that with increasing Sm doping, defects as well as \(V_B^{''''}\) related defects increase, while \(V_A^{''}\) and \($$V_o^{ \bullet \bullet }$$\) decrease. The correlation analysis between the variation of defects and the results of dielectric, piezoelectric and ferroelectric tests offers powerful and conclusive proof that defects contribute to the local structural heterogeneity as well as the variation of T_C. The variation of ferroelectric, dielectric and piezoelectric parameters with Sm-doping content is ascribed to the superposition effect of the contribution from \(Sm_{Pb}^ \cdot\) defects and the contribution from \($$V_A^{''}\,V_B^{''''}\,V_o^{ \bullet \bullet }$$\).