Accession Number : AD0787681

Title :   Concentration Dependent Diffusion of H(+) in TiO2: Analysis of Electronic Effects in Ionic Diffusion,


Personal Author(s) : Johnson,O. W. ; DeFord,J. W. ; Paek,S. H.

Report Date : JUN 1974

Pagination or Media Count : 20

Abstract : Diffusion of charged impurities or defects in a non-metallic crystal generally results in changes in the electron Fermi level relative to the lattice energy bands and impurity levels, thus producing substantial internal electric fields. These fields in turn exert a force on the diffusing ion, hence modifying the diffusion process. A self-consistent treatment describing such diffusion processes in materials with band gap = or > 1.5 eV is developed. The problem of interdiffusion of two similar ions (as in an isotope exchange experiment) is also analyzed. Detailed calculations for both single ion diffusion and interdiffusion of H and D in TiO2 are presented. Experiments leading to accurate determination of the field-free diffusion parameters for H in TiO2, both by the isotope exchange technique and by ionic conductivity measurements, are reported. In addition, single diffusion measurements have been carried out. Criteria for applicability of our analysis are discussed, as well as the relationship of this analysis to previous, more restricted treatments of the internal field problem. (Modified author abstract)

Descriptors :   *Diffusion, *Deuterium, *Hydrogen, *Titanium oxides, Impurities, Ions, Isotope exchange, Coefficients, Electrical conductivity, Crystal defects, Band theory of solids, Diffusion theory, Ionic current, Crystals

Subject Categories : Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE