材料期刊网

The phonon Raman spectra of Bi2Sr2Ca1-xRxCu2O8+delta (R = Pr and Gd) single crystals are systematically investigated. The experimental results show that the O(2)(Sr)A(1g) mode softens with Pr and Gd doping, while the O(1)(Cu) B-1g mode softens with Pr doping but hardens with Gd doping. The changes of average ionic radius on the Ca site in Bi-based cuprates can account well for the Raman frequency shifts of the O(I)(Cu) mode, but have little influence on the O(2)(Sr) mode. The frequency softening of the O(2)(Sr) mode in Pr- and Gd-doped Bi2212 crystals mainly results from contraction of the BiO bilayers with doping content. The correlation between the O(2)(Sr) mode frequency and the c-axis parameter as well as the incommensurate modulation wavelength is discussed.