NiMn2−xMgxO4 (0 ≤ x ≤ 0.4) ceramics have been studied by powder x-ray diffraction (XRD), infrared (IR) spectroscopy, and thermogravimetric analysis. NiMn2−xMgxO4 ceramics are all single-phase with spinel structure. XRD and IR spectroscopy results indicate that Mg2+ ions occupy A- and B-site of spinel lattice, which inhibits the formation of cation vacancies. Moreover, Mg2+ substitution enhances the tolerance of the oxidation in air. As a result, Mg substitution leads to a significant increase in ρ25, temperature coefficient of resistivity B25/85, and activation energy, which improves the aging property of NiMn2−xMgxO4 negative temperature coefficient thermistors.
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This research was financially supported by the Zhejiang Provincial Science Foundation (No. Y6110475) and the Zhejiang Provincial Fund of Science and Technology (Grant No. 2007C21003).
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Wang, J., Zhang, J. Effects of Mg substitution on microstructure and electrical properties of NiMn2−xMgxO4 NTC ceramics. Journal of Materials Research 27, 928–931 (2012). https://doi.org/10.1557/jmr.2012.29