The effective valences and non-dimensional number of C and N, for solid-state electrotransport in the  phase, were measured by using the tangent method. The electric field intensity was between 3.0 and 11.3V/m, the temperature was between 1223 and 1323K, the initial C content ranged from 0.1 to 0.9wt%, and the N content was equal to 0.025wt%. It was found that, at electric field intensities which were below 5.0V/m, the effective valence of C increased rapidly with decreasing electric field intensity while the non-dimensional number remained constant. At higher values, the effective valence of C was constant, and the non-dimensional number increased linearly with increasing field intensity. The temperature did not affect the effective valence or non-dimensional number of C. The effective valence and non-dimensional number of C decreased gradually with increasing C concentration. The effective valences of C and N increased slightly when both elements co-existed.

K.Kuroda, K.Kato, T.Fujisawa, C.Yamauchi: Journal of the Japan Institute of Metals, 1995, 59[12], 1247-52