STUDY ON COPPER VALENCY OF HIGH-TC SUPERCONDUCTOR YBA2CU3O7-Y BY HIGH-TEMPERATURE X-RAY ABSORPTION-SPECTROSCOPY

The X-ray absorption spectra of the Cu K-edge have been obtained for a high-T//c superconductor YBa//2Cu//3O//7// minus //y by in-situ high temperature measurements between room temperature and 600 degree C and for quenched samples prepared by rapid cooling from various temperatures up to 880 degree C. The results indicate that the copper valency is predominantly 2 plus and the monovalent state appears as the oxygen contents decrease with increasing temperature. The Cu K-edge X-ray absorption spectra of lanthanide compounds with oxygen-deficient triperovskite structure LnBa//2Cu//3O//7// minus //y pounds with oxygen-deficient triperovskite structure, LnBa//2Cu//3O//7// minus //y (Ln equals Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb or Lu) were also reported.