Abstract: The accepted doping ion in Ti⁴⁺-site of PZT-based piezoelectric ceramics is a well-known method to increase Q_m, since the acceptor coupled by oxygen vacancy becomes defect dipole, which prevent the domain rotation. A serious problem is that generally, Q_m decreases as the temperature (T) increases, since the oxygen vacancies is decoupled from the defect dipoles. Here, we report that Q_m of PSZT ceramics doped by 0.40% Fe₂O₃ (in mole), abnormally increases as T increases, which Q_m and d₃₃ at room temperature and Curie temperature T_C is about 507, 292 pC/N, and 345 ℃, respectively. The maximum Q_m of 824 was achieved around 120-160 ℃, which is 63% higher than the value at room temperature, while the dynamic piezoelectric constant d₃₁ was just slightly decreased by about 3.9%. XRD (X-ray Diffraction) and PFM (Piezoresponse Force Microscopy) results show that The interplanar spacing and the fine domains form as temperature increases, and the TSDC (Thermally Stimulated Depolarization Current) shows that the defect dipoles is stable up to 240 ℃, we think that the aggregation of oxygen vacancies near the fine domains and defect dipole which is stable up to 240 ℃, pin domain rotation, resulting in the enhanced Q_m in the increasing temperature. This result give a possibility to design a high Q_m in high temperature.

Key words: defect dipoles, temperature characteristic, oxygen vacancies, electro-mechanical properties, mechanical quality factor, hardening doping