Softening-hardening transition of electrical properties for Fe3+-doped (Pb0.94Sr0.05La0.01)(Zr0.53Ti0.47)O3 piezoelectric ceramics

Fe3+-doped (Pb0.94Sr0.05La0.01)(Zr0.53Ti0.47)O3 (PSL(ZT)1-x-Fex) piezoelectric ceramics were prepared by the solid-state reaction method and with a variation of the Fe3+ content. When the Fe3+ content was less than 0.010, the ceramics exhibited the features of soft piezoelectric ceramics with a large remnant polarization (Pr) of 35.7 μC/cm2, a large bipolar strain of 0.22% and a high piezoelectric coefficient (d33) of 412 pC/N. The number of oxygen vacancies increased and the domain walls were pinned by the defect diploes with a further increase of the Fe3+ content. Meanwhile, the PSL(ZT)1-x-Fex ceramics showed typical hard behavior and the mechanical quality factor Qm was as high as 500. The softening-hardening transition of electrical properties was also systematically analyzed by adjusting the oxygen vacancies, the space charges and the difference between the unipolar strain and the value of d33×E.