複酸化物からのLi_2Oの蒸発速度

概要

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Double oxides of Li_2O and M-metal oxides(i.e., NiO, Al_2O_3, SiO_2, Nb_2O_5 and WO_3)were synthesized from Li_2CO_3 and M-oxide or M-hydroxide starting powders, and studied with respect to their vaporization behavior under an air atmosphere. Vaporization losses per unit surface area(kg・m^<-2>)from sintered round pellets(1.35 cm in dia.×0.1-0.2 cm thick)of these oxides were measured in a flow of dry air(200 ml・min^<-1>). The vaporization rate(kg・m^<-2>・s^<-1>)R at the onset of vaporization from the original double oxide was obtained as a mean value between 0-1000 s. The logarithm of these rates at 900℃, log R, decreased linearly with increasing values of the Z/r×EN×M/Li product, where Z, r and EN correspond to valence, ionic radius and electronegativity for M, respectively. For the solid solution Li_xNi_<1-x>O, the specimen surface was covered with pure Li_2O during vaporization, because of Li_2O enrichment on the surface. Thus the above-mentioned product value corresponded to that for pure Li_2O. The slope of the straight line obtained on a log-log diagram of the vaporization loss as a function of time in the primary stage indicates an influence of the residual oxide layer covering the surface on Li_2O vaporization. The slope values increased with increasing temperature and Li_2O content in the double oxides. The slope values in the secondary stage depended on the progress of recrystallization of the residual oxide layer.
1998-07-01