Nano–Crystalline Mn–Ni–Co–O Thermistor Powder Prepared by Co–Precipitation Method

Abstract

Here, we demonstrate that nano–sized Mn–Ni–Co–O powder can be prepared at a low temperature via a co–precipitation method. In this work, Mn2+ was partially oxidized to Mn3+ ions in an aqueous solution by adding an oxidizing agent (H2O2). The co-presence of Mn2+ and Mn3+ cations enabled the precipitated products to be well-crystallized at a calcining temperature as low as 650 °C, forming a pure cubic spinel structure. The pellets fabricated from this calcined powder showed a relative density of up to 97.1% at a moderate sintering temperature of 1100 °C. Moreover, these ceramics exhibited electrical performance suitable for use in industrial thermistors, i.e., a room temperature resistivity (ρ25) of 1232 Ω cm, a thermistor constant (B25/85) of 3676 K, and an aging coefficient (ΔR/R) of 1.43%. High sintering activity as well as the excellent electrical properties of the ceramics was attributed to the fine-sized particles of the synthesized powder.