FABRICATION AND CHARACTERIZATION OF Ni–Mn–Si–Al–O NTC THERMISTOR AND ITS APPLICATION AS TEMPERATURE WIRE SENSOR

Abstract

A series of Al 2 O 3 substituted manganese oxide ceramic compounds, Ni 0:6 Si 0:2 Mn 2:2Àx Al x O 4 (0 • x • 0:6), were prepared by solidstate reaction route. The phase composition, microstructure, and electrical properties of compounds were studied. The results revealed that all the compounds were composed of cubic spinel structure without any other oxides. Besides they exhibited a linear relationship between logarithm of electrical resistivity ( ln ) and reciprocal of absolute temperature (1/ T) over a temperature ranging from room temperature to 300 ○ C, which indicated a negative temperature coefficient (NTC) characteristic. The B 25=85 constant was found to increase with the increase of Al 2 O 3 content. The B 25=85 values of the NTC Ni 0:6 Si 0:2 Mn 2:2Àx Al x O 4 thermistors for x ¼ 0; 0:1; 0:2; 0:3; 0:4, and 0.6 were 4581, 4612, 4680, 4875, and 5089 K, respectively. Finally, a new method to produce one meter long continuous fire wire sensors was also proposed.