• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.490-496
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• 2005

The electrical properties and stability of the varistors composed of ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_{2}$O$_{3}$-Dy$_{2}$O$_{3}$ system were investigated with sintering time in the range of 1$\~$3 h at 1350$^{\circ}C$ . As the sintering time was increased, the varistor voltage and leakage current increased, but the nonlinear exponent decreased. The varistors sintered for 1 h exhibited excellent nonlinearity, with a nonlinear exponent of 55.3 and a leakage current of 0.1 $\mu$A, whereas presented relatively low stability. The varistors sintered for 2 h exhibited not only high nonlinear exponent of 46.3, low leakage current of 0.3 $\mu$A, low dielectric dissipation factor of 0.0431, but also the highest stability, in which the variation rates of varistor voltage, nonlinear exponent, leakage current, dielectric constant, and dielectric dissipation factor were -3.0$\%$, -4.1$\%$, +3056.2$\%$, +5.1$\%$, and -12.5$\%$, respectively, after DC accelerated aging stress state of 0.95 V$_{1ma}$/150$^{\circ}C$/24 h. On the whole, the nonlinearity and stability of these varistors are greatly affected by the sintering time.