New high temperature NTC thermistors based on the Mg(Al1−xCrx)2O4 ceramics

•Mg(Al1-xCrx)2O4 ceramics have been fabricated by conventional sintering.•The NTC electrical properties of these ceramics have been investigated.•The resistivity decreases with increasing Cr content.•The decrease in the resistivity is due to the increase of Cr3+ and Cr4+ ions.•The ceramics could be suitable for high temperature NTC thermistor application.

The new high temperature negative temperature coefficient (NTC) ceramics based on the Mg(Al1-xCrx)2O4 compositions have been investigated. The ceramics were synthesized by conventional solid state reaction at 1650 °C. For 0 ≤ x ≤ 0.5, the X-ray diffraction analysis has revealed that the sintered ceramics crystallize in a cubic spinel structure. X-ray photoelectron spectroscopy analysis confirms the existence of Cr3+ and Cr4+ ions on lattice sites, which result in hopping conduction. The resistivity decreases with increasing the Cr content. The obtained values of ρ500 and B500/800 and Ea are in the range of 2.67 × 103–3.72 × 107Ωcm, 6731–11886 K, 0.581–1.025 eV, respectively. The electrical properties of these ceramics can be adjusted by the Cr content. Such ceramics could be suitable for high temperature NTC thermistor application.