EFFECT OF PHYSICAL AND CHEMICAL ADSORPTION OF WATER-MOLECULES ON YBA2CU3O7-DELTA SURFACE-COMPOSITION

The effect of physically and chemically sorbed water molecules on the elemental composition of the surface layer of YBa2Cu3O7-delta high tem perature superconductors with delta = 0.00 and 0.33 has been investiga ted. The physically sorbed multilayer of water molecules stimulates th e exchange of barium and copper ions between the surface and bulk of t he crystal lattice. The concentration of barium ions increases twofold and that of copper ions decreases twofold while the oxygen content re mains constant in the surface layer of YBa2Cu3O7-delta. Chemical adsor ption does not change the elemental composition of the surface layer. It is supposed that ion exchange is stimulated by the electric field o f ordered water dipoles in the multilayer. The values of electric fiel d strength and diffusion coefficient of ions are estimated.