Solution Synthesis of Cubic Spinel Mn-Ni-Cu-O Thermistor Powder.

Toward the development of NTCR thermistors, nanocrystalline Mn-Ni-Cu-O powder was synthesized from a mixed chloride aqueous solution by a simple co-precipitation method.The introduction of an oxidizing agent (HO) into the solution led to the partial oxidation of Mn ions into Mn ions, which enabled the collected powder to be well crystallized at 650 °C. Such a low calcining temperature resulted in fine particles with a mean size of 60 nm, which significantly promoted densification of the resulting ceramics. As a result, a dense and homogenous microstructure with a relative density up to 97.2% was achieved for pellets sintered at 1100 °C. Furthermore, these sintered ceramics exhibited a room temperature resistivity () of 67 Ω·cmand a thermistor constant () of 2843 K, which make them suitable for use in industrial thermistors. In addition, electrical stability was greatly improved when the ceramics were prepared by a new two-step sintering method. The results suggest that the co-precipitation route with the introduction of HO is suitable for the fabrication of cubic spinel thermistor nanopowders.