Electrical properties and temperature sensitivity of B-substituted CuO-based ceramics for negative temperature coefficient thermistors

Abstract

The ceramics of B-substituted Cu0.992Y0.008O (BYCO) with weight percentages of 0.25, 0.5, 0.75, 1.0 and 1.5 % of H3BO3 were prepared by a wet-chemical synthesis method, and the related phase component and electrical properties were investigated. All the ceramics have a monoclinic structure as that of CuO crystal. The BYCO ceramics have a typical characteristic of negative temperature coefficient (NTC) of resistivity over the temperature range from 25 to 300 °C, and the NTC materials constant (B 25/85) can be adjusted from 1112 to 4376 K by changing the H3BO3 content in BYCO ceramics. Investigations of complex impedance spectra revealed that the resistivities of the BYCO ceramics mainly result from the bulk effect, and both the bulk effect and grain boundary effect contribute to the NTC feature. Both the band conduction and electron-hopping models are proposed for the conduction mechanisms in the B-substituted CuO-based ceramics.