Characterization of electrical conductivity and temperature sensitivity of Cr/Sb-modified SnO2 ceramics

To develop new system of thermal-sensitivity materials with the feature of negative temperature coefficient (NTC) of resistivity, Sb-doped SnO₂ (ATO) and Cr-modified ATO (Sn_0.95−ySb_0.05Cr_yO₂ (y ≤ 0.05)) ceramics are prepared. The phase component of the ceramics is analyzed by X-ray diffraction, and microstructures are observed by scanning electron microscope. The electrical conductivity and temperature sensitivity of the ceramics are investigated by analysis of the related resistance–temperature feature and complex impedance spectra (CIS). The results show that the Cr-modified ATO ceramics have excellent NTC performance, and the NTC materials constants of the ceramics can be conveniently adjusted from 1500 to 4500 K by changing the concentrations of Cr-ions. The calibration equations are adopted to fit the resistance–temperature plots of Sn_0.93Sb_0.05Cr_0.02O₂ ceramic with the Matlab program, and the results show that the Hoge-3 equation with 5 parameters has good fitting effect, indicating that it can satisfy the programing requirement for a temperature sensor well. By analyzing the CIS at different temperatures, the conduction mechanisms of the Cr-modified ATO ceramics are discussed.