Connectivity between electrical conduction and electrode structure in Mn–Co–Ni–O thick-film thermistors

Abstract

In this paper, the electrical conduction of grain and grain boundary (GB) in Mn1.85Co0.3Ni0.85O4 negative-temperature-coefficient (NTC) thick-film thermistors with different finger electrode structures was studied carefully through the temperature-dependent ac impedance spectroscopy analyzing. It was found that the increase in finger length will drop the resistance of grain and GB sharply. The conduction mechanism of the grain was independent on the electrode structure and followed the small-polaron hopping model. However, the conduction mechanism of GB was dependent on the electrode structure. With the finger length increasing, the resistance–temperature (R–T) relation of GB was transformed from nonlinear to linear relation. These studies on the mechanisms concerning the dependence of conduction behaviors of grain and GB on electrode structure will provide a comprehensive understanding on the transformation behaviors of R–T relation of thick-film NTC thermistors.