The effect of ZnO content and sintering temperature on the electrical properties of Cu-containing Mn1.95-xNi0.45Co0.15Cu0.45ZnxO4 (0≤x≤0.3) NTC thermistors

The primary phase of sintered Mn1.95-xNi0.45Co0.15Cu0.45ZnxO4 (0 <= x <= 0.3) bodies was solid solutions of constituent oxides with a cubic spinel structure, along with NiO-rich Mn-Ni-Co-Cu-(Zn)-O oxides and Mn3O4. The density and grain size of the Mn1.95-xNi0.45Co0.15Cu0.45ZnxO4 samples increased with increasing ZnO content. The electrical properties of the negative temperature coefficient (NTC) thermistors were controlled by changing their composition. The incorporation of a small amount of ZnO (x <= 0.12) led to an increase in resistivity and the B-25/85 constant. The values of rho(25), rho(85), B-25/85 constant, and activation energy for the NTC thermistors sintered at 1025 degrees C were somewhat higher than those sintered at 1025 degrees C. The NTC thermistors with very low resistivities and moderate sensitivities to temperature excursions were fabricated at a wide range of sintering temperature (1025-1075 degrees C). (C) 2008 Published by Elsevier B.V.