Study of lonization Potential for Oxide Superconductors

The concept of mean ionization potential of crystal ＜U₀＞ is proposed, and the ＜U₀＞ of Oxide Superconduetors is investigated in this paper. The result shows, that the ＜U₀＞ values of almost all supercondueting oxides cencentrate in a narrow rarge from 10.20 to 10.50eV, while that of non-superconducting oxides scatter outside this region. This characteristics may be then as a new mark or criterion for oxide superconductivity. In Y（123）, the variation of oxygen content results in the increase of Tc upon increase of ＜ U₀＞, while the substitution of Ba2+ by Sr2+ results in the increase of Tc upon increase of ＜ U₀＞. However in both cases, the variation of Tc is caused by the change of ＜ U₀ ＞. So the mean ionization potential ＜ U₀ ＞ is closely correlated with the superconductivity of oxides.