Abstract
Bi-modified (Zn0.4Ni0.6)1-xNaxO (denoted as xZNN, x < 0.1) ceramics were prepared by conventional solid-state reaction process. The xZNN ceramics have rock-salt type structure. Besides the rock-salt phase, there is a monoclinic Bi2O3 secondary phase coexisting in the Bi-modified xZNN ceramics. These ceramics exhibit typical characteristic of negative temperature coefficient (NTC) of resistivity. The NTC material constants (B values) of all prepared ceramics are higher than 4000 K. The room temperature resistivity and B values can be adjusted in a large range by altering either or both content of Na-ions and Bi-ions. The effect of Bi2O3 addition is remarkable in term of enhancing sinter ability to reduce sintering temperature from 1350 °C to 1150 °C, and improving aging stability to drop resistance drift rate from 237 % to 1.8 %. Aging characteristic was discussed based on models of space charge distribution and interfacial barriers.
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