Temperature sensitivity of Fe-substituted SnO2-based ceramics as negative temperature coefficient thermistors

Abstract

Sb-doped SnO2 (ATO) and Fe-substituted ATO [Sn0.95−y Sb0.05Fe y O2 (y ≤ 0.10)] ceramics were prepared by using a wet chemical process followed by high-temperature solid reaction, and the related electrical conductivities were investigated. The analysis of X-ray diffraction indicates that all the prepared ceramics have a tetragonal crystal structure as that of rutile-type SnO2. The room-temperature resistivity ρ 25 of the Fe-substituted ATO increases with the Fe-content rising, and the Fe-substituted ATO ceramics show a typical characteristic of negative temperature coefficient (NTC) of resistivity. Compared with the ATO ceramics, the substitution of Fe can obviously adjust the materials constant B 25/85 as NTC thermistors. Fe-substituted ATO ceramics show high cyclic stability between room temperature and 250 °C. The investigations of electrochemistry impedance spectra reveal that the grain boundary effect is dominant in the NTC feature. Both the band conduction and electron-hopping models are proposed for the conduction mechanisms in the Fe-substituted ATO ceramics.