Preparation, characterization and electrical properties of spinel-type environment friendly thick film NTC thermistors

Environment friendly thick film NTC thermistors based on spinel-type semiconducting electroceramics of different compositions Mn1.85Co0.8Ni0.35O4, and Mn1.85Co0.8Ni0.35O4 + RuO2 were fabricated on alumina substrate. The basic bulk ceramics and the fired thick films were characterized by thermo-gravimetric analysis, X-ray diffraction, and scanning electron microscopy with energy depressive X-ray analysis. Thick film samples showed compact and homogeneous microstructure. The electrical parameters of the planar thick film NTC thermistors were determined. Depending on the ceramic composition, the prepared thick film NTC thermistors showed room temperature resistance in the range of 6–168 MΩ. The values of thermistor constant, β25/300 ranged from 3600 to 4900 K.