Oxidation of nickel and transport properties of nickel oxide

Point defect diagrams for pure and doped nickel oxide $$ {\hbox{N}}{{\hbox{i}}_{{1} - \delta }}{\hbox{O}} $$ in the temperature range of 1,173–1,673 K (II)

“…This could be caused by the influence of M 3+ ions on the concentration of the defects. Figure 1b presents the results of the calculations using the results of the studies by Sockel and Schmalzried [14],and Osburn and Vest [13]; also the results of Mrowec and Grzesik [21] are marked, and, as can be seen, are slightly higher. As illustrated in Fig.…”

“…Analyzing the results of the studies of the deviation from the stoichiometry by different authors [13,14,18,21] (see Fig. 1), it can be found that there are differences between them, but the dependence of δ on p O 2 has a similar character.…”

“…[9] Mrowec, Grzesik [16] [h • ] [20], (empty triangle)-Mrowec and Grzesik [21] by different authors can be thus caused mainly by a systematic error that relates to the method of the determination of the δ value. The value of ΔG o F obtained on the basis of the results of Sockel, Schmalzried [14], Osburn, Vest [13], Mrowec, and Grzesik [21], and the temperature dependence of ΔG o F was then determined. As a result of the calculations performed, it has been found that in the temperature range of 1,473-1,673 K, a good match of the dependence of the deviation from the stoichiometry on p O 2 to the experimental results of δ is obtained, taking into account only ½V 00…”

“…Due to the low concentration of point defects, it is assumed that they form an ideal solution. In order to determine the point defect structure at high temperatures, the studies on the deviation from the stoichiometry were performed by the following methods: electrochemical [14][15][16], thermogravimetric [13,[17][18][19][20][21], and via the studies of the electrical conductivity [10-13, 16, 17, 22-38]. The character of the dependence of the deviation from the stoichiometry on the oxygen pressure (the exponent close to ≈1/6) formed the basis for the thesis that in Ni 1Àd O, the dominating defects are double ionized nickel vacancies and electron holes.…”

“…There are discrepancies in the concentration of single ionized vacancies. The studies on the chemical diffusion [19][20][21][29][30][31][32][33][34][35][36][37][38][39][40][41] and of the self diffusion of nickel [19,[41][42][43][44][45][46], performed mainly at higher oxygen pressures, indicate that the matter transport in Ni 1Àd O occurs generally via double ionized nickel vacancies. A similar conclusion could be obtained from the relation between the concentration of defects, the diffusion coefficients, and the parabolic rate constants of nickel oxidation [21,[47][48][49][50][51].…”