Positron annihilation lifetime and Doppler broadening energy spectra were measured in Pr-containing Cu3Ba2YO7 at temperatures of between 18 and 295K. It was found that the defect-related positron lifetime component was independent of temperature for Cu3Ba2PrO7, and was very close to the value that was associated with bulk or defect-free material. The results indicated that the structure of this compound was almost free of defects which trapped positrons, and that there was an electronic structure change during cooling. There was a slight temperature dependence, below the superconducting transition temperature, in Cu3Ba2Pr0.5Y0.5O7. It was also found that a change in the positron Doppler line-shape parameter occurred at the superconducting transition temperature in the case of the 0.5Pr-containing compound but not in the case of the 1.0Pr-containing compound. The results showed that the average electron momentum at the annihilation sites increased as the temperature was lowered across the superconducting transition temperature in the case of the 0.5Pr-containing compound, but did not increase in the case of Cu3Ba2PrO7.

K.Jung, J.G.Byrne, M.C.De Andrade, M.B.Maple: Journal of Applied Physics, 1995, 78[9], 5534-9