Home – Home – Jornals – Chemistry for Sustainable Development 2006 number 4

The capability of YBa2Cu3Od for an intensive exchange with oxygen of a gas phase even at ambient temperature (ta) that has been detected previously has been studied with diversified physical methods. An X-ray photoelectron spectroscopy method has been applied to demonstrate that a degree of ionicity of cation-oxygen bonds increases during oxidation under the ta conditions. Along with this phenomenon, oxygen appears in a state that is close to chemically unbonded. This correlates with evidence on spontaneous electric polarization that emerges in yttrium-baric cuprate under the test conditions. The obtained result has been explained in the context of YBa2Cu3Od model as of a virtual ferroelectric, the critical temperature of which in certain conditions can grow up to high positive values. In so doing, modification of chemical state of [BaO2] structural group occurs from formal peroxide to formal oxide with strengthening of a certain Ba