A study on the role of Oxygen in the inelastic behaviour of YBa2Cu3O7 − x

The inelastic behaviour of YBa 2 Cu 3 O 7 − x has been investigated by the vibrating reed technique in the 300–900 K range. In particular the mobility of oxygen and its contribution to the inelastic spectra, measured both in isochronal and isothermal conditions, was studied by testing samples with different initial oxygen contents. Two inelastic peaks of relaxational type were observed at approximately 560 and 680 K associated to stress induced reorientation of structural defects. The relaxation strenght in both cases strongly depends on the oxygen content. The dynamic modulus shows anomalous behaviour at temperatures higher than 740 K where the orthorombic to tetragonal transformation sets up. Some hypothesis on the inelastic behaviour of YBa 2 Cu 3 O 7−x in terms of oxygen content, thermally activated diffusional jumps and structural transformations are discussed.