Formation and Sintering Characteristics of ZnMn₂O₄-type Spinels Using IZC Powder Recycled from the Waste of Used Dry Batteries

抄録

ZnMn₂O₄ spinel ceramics with NTC character were fabricated using a powder recycled from used dry batteries. The recycled powder (IZC) consisting of oxides of Zn and Mn as major solid phases was mixed with given amounts of hydrous MnCO₃ and heated in the temperature range 900°C-1300°C. The ZnMn₂O₄ spinel powders were produced from mixtures with mass ratio of MnCO₃/IZC larger than 1/2 above 900°C. The densification of the spinel powders thus obtained was considerably improved by washing the starting IZC powder with distilled water, which substantially reduced the concentrations of K, S and Cl components contained as impurities. Among oxide additives used to modify the densification and/or electrical properties of the spinel ceramics, the NiO additive (5 mass%) caused a drastic lowering in the electrical resistivity of the spinel sample by about four orders of magnitude at room temperature. Thus, the NiO-doped spinel ceramics obtained from a recycled IZC powder could be applied to a practical NTC thermistor with B=5650 K.