The effect of Zn on the microstructure and electrical properties of Mn1.17-xNi0.93Co0.9ZnxO4 (0 ≤ x ≤ 0.075) NTC thermistors

As-sintered Mn1.17-xNi0.93Co0.9ZnxO4 (0 <= x <= 0.075) bodies consisted of two phases: a major Mn-rich phase with a cubic spinel structure and a minor NiO phase with a cubic structure. The Mn1.17-xNi0.93Co0.9ZnxO4 ceramics were highly dense, ranging from 96 to 98% of the theoretical density and were microscopically homogeneous. The addition of Zn did not cause much change in the grain size and porosity. The obtained rho(25), B-25/85 constant, and activation energy of the negative temperature coefficient (NTC) Mn1.17-xNi0.93Co0.9ZnxO4 thermistors were in the range 1145-3696 Omega cm, 3218-3550 K, and 0.277-0.306 eV, respectively. This means that the electrical properties can be adjusted to desired values, depending on their Zn content. In particular, the resistivity and sensitivity were substantially enhanced with increasing Zn content. 2008 Elsevier B.V. All rights reserved.