A comparative study of different oxidation states of raw materials on the properties of a novel medium-entropy Co2.77Mn1.71Fe1.10Zn0.42O8 thermistor materials

In recent years, high entropy oxides (HEOs) have aroused extensive attention due to their potential applications in catalysis, energy storage and thermal protection. However, as an emerging material, the synthesis, properties and applications of HEOs have yet to be further developed. Herein, we reported a novel non-equiatomic medium-entropy Co2.77Mn1.71Fe1.10Zn0.42O8 oxides for temperature sensing applications by using the different oxidation states of cobalt and iron as raw materials. Results indicate that the prepared multi-component samples present a pure spinel phase, highly dense microstructure, and typical negative temperature coefficient characteristics. Our results also suggest that the different oxidization states of cobalt and iron of raw materials induce obvious influences on resistivity and aging stability. In particular, the medium-entropy oxides can exhibit excellent superior aging stability (the resistance drift ≤0.2% after accelerated aging in 125 °C for 600 h) by a suitable selection of the starting oxides. This work will provide new material design strategies for sensors or other electronic devices and guidance on the raw material selection from laboratory research to industrial production processes. A novel non-equiatomic medium-entropy Co2.77Mn1.71Fe1.10Zn0.42O8 oxides with purified spinel structure and superior aging stability have been successfully fabricated. Also, the different oxidization states of starting oxides induce influences on the electrical properties. [Display omitted] •A novel medium-entropy Co2.77Mn1.71Fe1.10Zn0.42O8 ceramics with pure spinel structure were successfully fabricated.•The prepared samples exhibit highly dense microstructure (ρrelative > 93%) and superior long-term stability (ΔR/R0 ≤ 0.2%).•The ceramics synthesized by Co2O3&Fe3O4 exhibit higher resistivity, and aging coefficient.