HIGH-TEMPERATURE EQUILIBRIUM BETWEEN HIGH-TC OXIDE AND GAS-PHASE - THE ROLE OF ELECTRONS AND HOLES

The equilibrium between the high-T(c) oxide YBa2Cu3O7-sigma and the gas phase is studied for some models of the ionic and electronic (e.g., two-band model) systems of the compound. The calculations show that the contribution of the electron-hole system to this equilibrium is essential. The comparison of the theory with experiment allows to obtain such parameters as binding energy of oxygen ions, their effective Einstein frequency OMEGA, the hole effective mass m(p), etc., the OMEGA and m(p) values being in agreement with those reported elsewhere. A number of relations, e.g. the electron and hole concentrations versus oxygen pressure P(o)2 and T, as well as the influence of doping (with donors or acceptors) on these relations and on the oxygen content are predicted using the parameters obtained. The region of high P(o)2 is also studied.