Effects of MnO2 addition on piezoelectric and ferroelectric properties of PbNi1/3Nb2/3O3-PbTiO3-PbZrO3 ceramics

High-density 0.5PbNi(1/3)Nb(2/3)O(3). 0.345PbTiO(3). 0.155PbZrO(3) (0.5PNN. 0.345PT.0.155PZ) ceramics were prepared by normal sintering with the additi on of 0-3.66 mol% MnO2 and their piezoelectric and ferroelectric properties were investigated. The effect of MnO2 addition on significantly lowering t he value of tan delta in the range of 0.37 to 0.93 mol% was proven. The low est value (= 0.37%) of tan delta was obtained in ceramics with 0.75 mol% Mn O2. Electromechanical coupling factors, k(p) and k(31), and the piezoelectr ic constant, d(31), decreased with increasing amount of MnO2 addition. The highest values of k(p), k(31) and d(31) were 0.66, 0.38 and - 362 pC/N, res pectively, and were obtained in the ceramics without MnO2, The effect of Mn O2 addition on improving the value of the mechanical quality factor, Q(m), was proven in the range of 0.93 to 1.85 mol% and the improvement was around twenty times that of the sample without MnO2, The distortion in the shape of P-E hysteresis loops for samples with MnO2 addition suggested that oxyge n vacancies formed by substituting Mn3+ ions for B-site ions (e.g., Ti4+ an d Zr4+ ions) in the perovskite structure partially inhibited the polarizati on reversal in the ferroelectrics. 0.5PNN.0.345PT.0.155PZ ceramics with 0.7 5-0.93 mol% MnO2 show great promise as practical materials for piezoelectri c applications.