A positron annihilation study of the Y-Ba-Cu-O compounds

The Doppler broadening technique of positron annihilation was used to investigate the electronic structure of the Y-Ba-Cu-O compounds in the range 85-300 K. Anomalous behaviour of the lineshape parameters with a change in temperature was observed, which shows a very distinct difference from the behaviour of superconducting alloys. The results suggest that the mechanism of the new oxide superconductors is different from that in the alloy systems.