Abstract
New high temperature negative temperature coefficient (NTC) thermistor ceramics based on a xMgAl2O4–(1 − x)YCr0.5Mn0.5O3 (x = 0.1, 0.4, 0.6) composite system have been successfully fabricated through spark plasma sintering (SPS) with a low sintering temperature and a short sintering period. The X-ray diffraction analysis indicates that the SPS-sintered composite ceramics consist of a cubic spinel MgAl2O4 phase and an orthorhombic perovskite YCr0.5Mn0.5O3 phase isomorphic to YCrO3. The SPS-sintered composite ceramics have high relative density ranging from 94.1 to 97.4% of the theoretical density. X-ray photoelectron spectroscopy analysis corroborates the presence of Cr3+, Cr4+, Mn3+, and Mn4+ ions on lattice sites, which may result in the hopping conduction. The obtained ρ25, B25–150, and B700–1000 of the SPS-sintered composite NTC thermistors are in the range of 1.53 × 106–9.92 × 109 Ω cm, 3380–5172 K, and 7239–9543 K, respectively. These values can be tuned by adjusting the MgAl2O4 concentration.
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