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.