The non-metal-metal transition of Bi 2Sr 2Ca 1−xY xCu 2O 8+δ studied by soft x-ray emission spectroscopy

Abstract

Cu L α,ß and O k α x-ray emission spectra and the measurements of the occupancy of Cu 3d orbitals in Bi 2Sr 2Ca 1−xY xCu 2O 8+δ are presented. No appreciable change in the valency of Cu is found with increasing x. In contrast to La 2− ySr yCuO 4 and YBa 2Cu 3O 6+y, when going from non-metal to metal, the high-energy shift of O K α band, caused by redistribution of the O 2p states of the apical oxygen atoms, is not observed. The valence states of Cu and O do not essentially redistribute due to Ca doping and the p-d energy separation does not change.