Reducing Sintering Temperature While Optimizing Electrical Properties of BCZT-Based Lead-Free Ceramics by Adding MnO₂ as Sintering Aid

In order to reduce the sintering temperature, MnO₂ was used as a sintering aid to prepare [(Ba_0.85Ca_0.15)_0.999(Dy_0.5Tb_0.5)_0.001](Zr_0.1Ti_0.9)O₃-x mol% MnO₂ (BCDTZT-x mol% MnO₂, x = 0.05, 0.2, 0.4, 0.6, 0.8, 1, 1.5, 3) lead-free piezoelectric ceramics in which the effects of the MnO₂ doping amount and sintering temperature on the phase structure, sintering behavior, and electrical properties of the BCDTZT-x mol% MnO₂ ceramics were systematically analyzed. All ceramics have a single perovskite structure and coexist in multiple phases. The optimal sintering temperature was reduced from 1515 °C to 1425 °C, and the density of all ceramics was increased as compared with the undoped ceramic, reaching a maximum of 5.38 g/cm³ at x = 0.8 mol%. An appropriate MnO₂ doping amount of 0.4 mol% could effectively suppress oxygen vacancies and improve electrical properties, resulting in the best comprehensive performance of the ceramics, with a dielectric constant maximum of 12,817, a high piezoelectric constant of 330 pC/N, and good strain value (S_max = 0.118%) and low strain hysteresis (Hys = 2.66%). The calculation of activation energy indicated that the high-temperature conductivity was dominated by oxygen vacancies in all ceramics. The results showed that the appropriate introduction of MnO₂ as a sintering aid could improve the performance of BCZT-based ceramics while reducing the sintering temperature, presenting high practical application value in the fields of low electric field sensors and actuators.