Effect of Na_2O and B_2O_3 Addition on Nonlinear Electrical Properties of WO_3-Based Capacitor-Varistors

摘要

WO_3-based varistors with added Na_2O and B_2O_3 were synthesized by the solid-state reaction. The undoped and B_2O_3-doped WO_3 ceramics exhibited weak nonlinear Ⅰ-Ⅴ characteristics. The nonlinear Ⅰ-Ⅴ characteristics of the ceramics increased slightly after the addition of Na_2O and more significantly after the addition of Na_2O and B_2O_3. The nonlinearity coefficients α of the WO_3, Na_(0.005)WO_3, and Na_(0.005)WO_3-5 wt % B_2O_3 ceramics were 1.86, 2.03, and 5.22, respectively. The breakdown voltages of the WO_3, Na_(0.005)WO_3, and Na_(0.005)WO_3-5 wt % B_2O_3 ceramics were 1.56, 6.05, and 12.42 V/cm, respectively. The dielectric constant and the dielectric loss of the Na_(0.005)WO_3-5 wt % B_2O_3 ceramic were ～50-150 and less than 0.3, respectively, for frequencies ranging from 1 to 1000 kHz.