Characterization of electrical conductivity and temperature sensitivity of Cr/Sb-modified SnO 2 ceramics
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Characterization of electrical conductivity and temperature sensitivity of Cr/Sb‑modified SnO2 ceramics Weiqin Yan1 · Hong Zhang1 · Xianchi Wang1 · Chang You1 · Zhicheng Li1 Received: 19 November 2019 / Accepted: 20 January 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract To develop new system of thermal-sensitivity materials with the feature of negative temperature coefficient (NTC) of resistivity, Sb-doped S nO2 (ATO) and Cr-modified ATO ( Sn0.95−ySb0.05CryO2 (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 Sn0.93Sb0.05Cr0.02O2 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.
1 Introduction Negative temperature coefficient (NTC) thermistor is a kind of electronic component whose resistivity decreases with the increase of temperature. NTC thermistor has the characteristics of high sensitivity and good interchangeability. It is a key component for temperature measurement and control, temperature compensation, suppression of current surge, infrared detection, and so on. It has been widely used in daily life, national economy, military, aerospace, and other fields [1–3]. At present, NTC thermistors, which are mostly used in research and practice, are semiconductor materials with AB2O4 spinel structure composed of transition metal oxides. The conduction mechanism of NTC spinel compounds is generally accepted by the small polaron hopping model, in which charge carriers hope between the cations locating at the octahedral B-sites such as Mn3+–Mn4+ ions in spinel manganates. The exact oxidation state of the Mn-cations in spinel structure obviously depends on sintering conditions, including sintering temperature, oxygen partial pressure, and procedures. Therefore, minor changes in sintering condition * Zhicheng Li [email protected] 1
School of Materials Science and Engineering, Central South University, Changsha 410083, China
may result in significant difference in the valences of the B-site cations and affect the electrical properties [4–6]. Compared with the NTC thermistors based on the spinel materials, the ones based on simple semi-conductive oxides have significant advantages [7–13]: The effect
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