A new family of Pb-based 1222 cuprates Pb(Sr,La) 2Ln 2Cu 2O z (LnGd, Dy, Eu, and Pr)

Abstract

A series of new Pb-based 1222 cuprates of the general formula Pb(Sr,La) 2Ln 2Cu 2O 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., Pb 4+ and Pb 2+, and the proportion of Pb 4+ and Pb 2+ is close to 1:1. The Pb-1222 phases Pb(Sr 2− x La x )Ln 2Cu 2O 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°C in air for the composition Pb(Sr 1.2La 0.8)Gd 2Cu 2CO z . All these Pb-1222 phases are not superconducting.