VALENCE FLUCTUATION AND ITS EFFECT ON THE SYNTHESIS, STRUCTURE AND PROPERTIES OF COMPOUNDS

The valence fluctuations of terbium and europium were studied using in situ electrical resistance measurement under high pressure and high t emperature, X-ray diffraction, X-ray photoelectron spectra and Eu emis sion spectra. The synthesis process of CeTbO3 under high pressure can be marked by the valence fluctuation of Tb4+ --> Tb3+. The relationshi p between the intensity ratio, I, of the higher binding energy peak to the lower one and the content ratio, Z, of Tb4+/Tb in Tb4d photoelect ron spectra can be described by the equation I = -0.98Z2 + 2.15Z (0 le ss-than-or-equal-to Z less-than-or-equal-to 1). Using this equation th e valence state of terbium and its effect on the superconductivity in Eu1-xTbxBa2Cu3O7-delta were investigated. In addition, the phenomenon of pressure-induced valence fluctuation was also observed in the SrB2O 4:Eu system.