High-temperature vaporization of Li2O component from solid solution LixNi1-xO in air

The vaporization experiments for Li2O component from disk type specimens of the solid solution Li2Ni1-xO (x less than or equal to 0.4) (materials for the fuel cell) were carried out in flowing air (1 cms(-1)) in the temperature range 400-700 degrees C. Log-log plots of the vaporization vs time consisted of two or three straight lines with different slopes (0.2-0.97). The smaller slopes at 500-600 degrees C, as shown later, suggest a growth of concentration gradient of Li2O. The slope at the second stage increased to unity with an increase in x from the starting value and with lowering temperature for the same x. The vaporization stopped at the third stage, leaving some Li2O behind. From considerations of the change in x-value with time, a formation of a Li2O concentration gradient in the specimen, and an activation energy for the vaporization, a formation reaction of Li2O2(g) from Li2O(c) decomposed from the solid solution and its diffusion rate in the specimen are supposed to be rate-determining. (C) 1997 Elsevier Science Limited and Techna S.r.l.