Abstract
High-density 0.5PbNi1/3Nb2/3O3⋅0.345PbTiO3⋅0.155PbZrO3 (0.5PNN⋅0.345PT⋅0.155PZ) ceramics were prepared by normal sintering with the addition of 0-3.66mol% MnO2 and their piezoelectric and ferroelectric properties were investigated. The effect of MnO2 addition on significantly lowering the value of tan δ in the range of 0.37 to 0.93mol% was proven. The lowest value (=0.37%) of tan δ was obtained in ceramics with 0.75mol% MnO2. Electromechanical coupling factors, kp and k31, and the piezoelectric constant, d31, decreased with increasing amount of MnO2 addition. The highest values of kp, k31 and d31 were 0.66, 0.38 and -362pC/N, respectively, and were obtained in the ceramics without MnO2. The effect of MnO2 addition on improving the value of the mechanical quality factor, Qm, was proven in the range of 0.93 to 1.85mol% 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 oxygen vacancies formed by substituting Mn3+ ions for B-site ions (e.g., Ti4+ and Zr4+ ions) in the perovskite structure partially inhibited the polarization reversal in the ferroelectrics. 0.5PNN⋅0.345PT⋅0.155PZ ceramics with 0.75-0.93mol% MnO2 show great promise as practical materials for piezoelectric applications.
