Abstract
Y2O3-doped Zn1-xNi x O (x = 0, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.9) powders were prepared by a wet chemical synthesis method, and the related ceramics were obtained by the traditional ceramic sintering technology. The phases and related electrical properties of the ceramics were investigated. The analysis of X-ray diffraction (XRD) indicates that the prepared ceramics with Ni substitution have a cubic crystalline structure. The resistance–temperature feature indicates that all the ceramics show a typical effect of negative temperature coefficient (NTC) of resistivity with the thermal constants between 3998 and 5464 K, and have high cyclical stability in a temperature range from 25 to 300 °C. The impedance analysis reveals that both grain effect and grain boundary effect contribute collectively to the NTC effect. The electron hopping and band conduction models are proposed for the grain (bulk) conduction, and the thermally activated charge carrier transport overcoming the energy barrier is suggested for the grain boundary conduction.
Highlights
Negative temperature coefficient (NTC) thermistors are widely used in industrial and domestic devices
The NTC thermistors for the commercial applications are always the solid solutions based on the transition metal oxides and have the spinel structure, such as Mn–Ni–O, Ni–Cu–Mn–O, and Mn–Co–N–O systems [1,2]
One weak X-ray diffraction (XRD) peak can be detected at 2θ ≈ 29.23° as denoted by symbol ‘‘♦’’; the weak XRD peak might be the one from Y2O3
Summary
Negative temperature coefficient (NTC) thermistors are widely used in industrial and domestic devices. One of the distinct advantages of the semiconductive oxides used for the NTC applications is that the room-temperature conductivity can be effectively adjusted by element doping and the related thermal-sensitive constants can be improved by substituting suitable impurities [17,18,19,20]. Where T is the resistivity at temperature T, T is the temperature in Kelvin, k is the Boltzmann constant, A is a constant related to the material characteristic, Ea is the activation energy of conduction, and B is the NTC
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