Ta_2O_5与Nb_2O_5对TiO_2基压敏陶瓷电性能的影响

INFLUENCE OF Ta_2 O_5 AND Nb_2 O_5 ON ELECTRICAL PROPERTIES OF TiO_2-BASED VARISTOR CERAMICS

研究了Ta2O5与Nb2O5对TiO2基压敏陶瓷电性能的影响.按照配方TiO2+0.003(按摩尔计)(SrO+Bi2O3+SiO2)+x Ta2O5+yNb2O5配制3种组分的圆片试样,各组分摩尔量分别为:x=0.000 75,y=0;x=0.000 375,y=0.000 375及x=0,y=0.000 75.采用电流-电压、电容测量、阻抗分析和势垒高度测量等实验手段,分析了Ta2O5和Nb2O5的作用机理.结果发现,x=0.000 75的样品显示出最低的压敏电压梯度(E10 mA=7.9 V/mm)和最大的表观介电常数(εra=5.88×104),y=0.000 75的样品显示出最高的压敏电压梯度(E10mA=48.9 V/mm)和最小的表观介电常数(εra=1.39×104).这表明,掺Ta2O5可有效地降低压敏电压,提高介电常数.

The electrical properties of TiO2-based varistor ceramics doped with Ta2O5 and Nb2O5 were studied. Test samples were prepared with the formula of TiO2 + 0.003 (in mole, the same below) (SrO + Bi2O3 + SiO2) + xTa2O5 + yNb2O5, where x=0.00075, y=0; x=0.000375, y=0.000375 and x=0, y=0.00075 respectively. Based on the results of measurements of electric current-voltage and capacitance, impedance analysis and barrier height measurement, the working mechanism of Ta2O5 and Nb2O5 was analyzed. It is found that the sample of x=0.00075 exhibits a lowest breakdown voltage gradient (E10mA) of 7.9 V/mm and a biggest apparent dielectric constant of 5.88 × 104, while the sample of y=0.00075 exhibits a highest breakdown voltage gradient (E10 mA) of 48.9 V/mm and a smallest apparent dielectric constant of 1.39 × 104. It shows that the doping of Ta2O5 can reduce the breakdown voltage gradient and raise the apparent dielectric constant effectively.