PbNi_1/3Nb_2/3O₃-PbTiO₃-PbZrO₃系セラミックスの圧電及び強誘電特性に及ぼすMnO₂添加の影響

抄録

High-density 0.5PbNi_1/3Nb_2/3O₃⋅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, k_p and k₃₁, and the piezoelectric constant, d₃₁, decreased with increasing amount of MnO₂ addition. The highest values of k_p, 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, Q_m, 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.