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

The new high temperature negative temperature coefficient (NTC) ceramics based on the Mg(Al1-xCrx)(2)O-4 compositions have been investigated. The ceramics were synthesized by conventional solid state reaction at 1650 degrees 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 rho(500) and B-500/800 and E-a are in the range of 2.67 x 10(3) -3.72 x 10(7) Omega cm, 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. (C) 2016 Elsevier B.V. All rights reserved.