Hydrothermal synthesis and electrical properties of Co–Mn–Fe–Zn–O NTC nanopowder materials

The research on the best technology of large-scale hydrothermal preparation of Co–Mn–Fe–Zn–O (CMFZ) material will provide reference for its industrial production. The CMFZ nanopowders were prepared on a large scale by hydrothermal method to explore the optimal process to obtain NTC ceramic materials with high consistency. The precursor morphology showed that their grain sizes were small, and with the increase of reaction temperature, reaction time, and stirring speed, the grain size of the powder first decreased to 20.01 nm and then increased to 36.56 nm, and the grain size of the corresponding ceramic samples also decreased and then increased. The optimum preparation conditions at 150 °C for 9 h and stirring speed of 200 rpm resulted in the smallest precursor grain size of 20.01 nm and the highest room-temperature resistivity ρ₂₅ and material constant B_25/50 of 1.44 kΩ cm and 3953 K, respectively, with average deviations of 0.089 and 0.237, indicating that the consistency of electrical properties were better. The study of the optimum technique for the large-scale hydrothermal preparation of CMFZ materials will provide a reference for their industrial production.