PRESSURE EFFECTS ON T-C AND STRUCTURE IN OVERDOPED TLSR2CACU2O7-DELTA

The effects of pressure on T-c and structure in overdoped T1Sr(2)CaCu( 2)O(7-delta) have been investigated. For superconducting samples dT(c) /dp is small and negative with d In T-c/dp varying from -0.016 GPa(-1) to -0.006 GPa(-1). There is no significant difference in the lattice compressibilities for superconducting and nonsuperconducting metallic samples suggesting that they are not sensitive to differences in defec t concentration or doping level. For the apical Cu-O(2) bond, in contr ast, the compressibility is about three times as large as that for the c-axis lattice parameter in the nonsuperconducting sample, while it i s nominally equal to the c-axis compressibility for the superconductin g sample. This may imply a difference in the amount of carriers transf erred into the CuO2 plane under pressure.