Fabrication and NTC Characteristic of Oxide Spinel Solid Solutions Containing Zn, Mn and Al from the Waste of Dead Batteries

Oxide spinels containing Zn, Mn and Al were synthesized from powder mixtures of Al(OH)3 and IZC (Itomuka zinc calcine), the latter of which is derived from the waste of dead batteries and consists of ZnO and MnO. Heating of the powders with different Al2O3/(ZnO+MnO) molar ratio (A/I value) ranging from 0.44 to 0.88 resulted in the formation of a single phase of spinel solid solution above 1000°C. The lattice parameter of the spinel s. s. with different cation ratios decreased almost linearly with increasing Al2O3 content. The chemical formulae of the solid solutions were estimated to be Zn(II)0.74Mn(II)0.26Mn(III)0.60Al(III)1.40O4 and Zn(II)0.50Mn(II)0.50Mn(III)0.09Al(III)1.91O4 for the samples with A/I=0.44 and A/I=0.88, respectively. Sintering of spinel powders calcined at 1100°C was enhanced at 1450°C to produce densified spinel ceramics with 90-93% of theoretical density. The addition of 4 mass%B2O3 or 4mass% Bi2O3 to synthesized powders caused the sintering temperature at which highly densified bodies were obtainable to be substantially lowered down to 1200°C, without any appreciable effect on the electrical properties of the sintered samples. The spinel s. s. ceramics having a composition of A/I=0.66 showed a negative linear temperature dependence of electrical resistivity with a thermistor constant (B) of 3240-3390 K.