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A simple negative temperature coefficient (NTC) thermistor material ZnO has been synthesized by mechanical alloying. The structural and microstructural properties were investigated by X-ray diffraction and field emission scanning electron microscopy. The electrical properties have been investigated in the temperature and frequency range of 300–500 °C and 100 Hz–1 MHz, respectively. The synthesized sample shows typical NTC behavior in the studied temperature and frequency range. The suitability of the material for thermistor application was analyzed by Steinhart–Hart equations and different thermistor parameters like sensitivity, temperature coefficient of résistance, activation energy and stability factor were calculated. The variation of resistance with temperature follow an exponential behaviour and well matched with Steinhart–Hart equation. It shows the sensitivity (β) value of 8079.93 K and the capability of mechanically alloyed zinc oxide for NTC thermistor application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr doped ZnO (Zn 1-x Cr x O) nanoceramics with different doping concentration were synthesized by high energy ball milling. • After 10hr ball milling upto 4% Cr can be doped into ZnO. • EDX and XPS analysis confirms the purity of the samples. • The variation of real and imaginary impedance with frequency shows the NTCR behavior of the sample. • The circuit model of ZnO and Zn 1-x Cr x O is a parallel combination of R-C model. Here, High Energy Ball Milling (HEBM) is used to prepare Cr doped ZnO (Zn 1-x Cr x O, x = 0–0.04) nanoceramics and their electrical behaviour is studied in detail. The X-ray diffraction suggests a hexagonal wurtzite structure. The Rietveld refinement XRD pattern of the sample calcined at 900 °C suggests that up to 4 at% of Cr can be doped into the ZnO structure. After sintering, the growth in the particle size was observed for Cr doped ZnO samples. The complex impedance behaviour of samples suggests a decrease in resistance with temperature. This shows the Negative Temperature Coefficient of Resistance (NTCR) characteristic of the Cr doped ZnO sample in the studied temperature range (300–500 °C). At higher temperature, the electrical relaxation behaviour is of the non-Debye type as observed from the relaxation time distribution. The equivalent electrical circuit of ZnO and Cr doped ZnO ceramic samples are a parallel arrangement of bulk capacitance (C b) and bulk resistance (R b). [ABSTRACT FROM AUTHOR]