Thermistors with negative temperature coefficient (NTC) of resistivity are
important components for temperature sensors and actuators. High material
constant (B value) of NTC thermistor, i.e. high-temperature sensitivity, is
one of key focuses. Herein, Bi/Mg modified NiO based ceramics for NTC
thermistors were prepared by conventional solid-state reaction method.
Introduction of Bi2O3 significantly enhances the sintering ability of
ceramics and reduces the sintering temperature from 1380 to 1250?C.
Mg-doping (i.e. preparation of Ni1-xMgxO ceramics, where x=0, 0.02, 0.05,
0.07 and 0.1) has significant effect on room temperature resistivity (?25).
Phase composition, microstructure, electrical property and electrical
stability were investigated. All prepared ceramics have the phase with
rock-salt structure and show typical NTC characteristics with B values
higher than 5300K. The electrical stability with an optimized
resistance-change rate of 1.02%after being aged at 150?C for 500 h is
achieved. The electrical properties of the ceramics were analysed by
combining X-ray photoelectron spectra with complex impedance spectra.