材料期刊网

A series of new Pb-based 1222 cuprates of the general formula Pb(Sr,La)(2)Ln(2)Cu(2)O(z) (Ln=Gd, Dy, Eu, and Pr) has been reported in this paper. In this kind of compounds, cations in the rock-salt-type monolayer completely consist of Pb ions, but the iodometric titration results indicate that the Pb ions in the rock-salt-type monolayer actually exist in the form of mixed valence states, i.e., Pb4+ and Pb2+, and the proportion of Pb4+ and Pb2+ is close to 1:1. The Pb-1222 phases Pb(Sr2-xLax) Ln(2)Cu(2)O(z) are very sensitive to sintering temperature and atmosphere, as well as the Sr content. For example, pure Pb-1222 can be only obtained at 920 degrees C in air for the composition Pb(Sr1.2La0.8) Gd2Cu2Oz. All these Pb-1222 phases are not superconducting.