Electrical properties and temperature sensitivity of Mo-modified MnFe2O4 ceramics for application of NTC thermistors

The Mo modified MnFe2O4 (MnFe2-x Mo (x) O-4, x <= 0.05) powders were prepared by using a wet-chemical synthesis method and the related ceramics were obtained by a traditional ceramic sintering technology. The effect of Mo contents on the phase component and related electrical properties of the ceramics were investigated. The results show that the prepared ceramics have a spinel-type cubic crystalline structure, and show a typical characteristic of negative temperature coefficient (NTC) of resistivity. The thermal sensitivity constants are around 6100 K over a wide temperature range from 25 to 250 A degrees C. The analysis of impedance spectra reveals that both grain effect and grain boundary effect contribute to the NTC feature. The conduction mechanisms for the ceramics are mainly proposed to be the electron hopping conduction inside the grains and the thermally activated charge carrier transport by overcoming the energy barrier for the grain boundary conduction.