ac hopping admittance in spinel manganate negative temperature coefficient thermistor electroceramics

Abstract

In this work, the ac admittance of a thick film nickel manganate spinel negative temperature coefficient thermistor ceramic system containing a glass phase is investigated. The dominating relaxation process is a grain boundary (GB) effect and has been investigated comprehensively. We present double-logarithmic plots of the specific admittance vs and (/dc) vs , and specific impedance z vs −z/ and [(dc/z)−1] vs , in order to characterize GB charge transport. Using the complex admittance notation (*), an unusually low Jonscher exponent of frequency ~0.007 was obtained and the GB relaxation displayed close to ideal behavior