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 2.2-x Al x O 4(0 ≤ x ≤ 0.6), were prepared by solid-state 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 ρ) 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 B25/85 constant was found to increase with the increase of Al 2 O 3 content. The B25/85 values of the NTC Ni 0.6 Si 0.2 Mn 2.2-x Al x O 4 thermistors for x = 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.