A SIMS study of oxygen tracer diffusion and surface exchange in La0.8Sr0.2MnO3+δ

Oxygen Isotope Exchange in Nanocrystal Oxides

“…The grain boundary diffusion activation energy Q GB was found to be 1.95 eV. Using the data of study (De Souza et al, 2000) for volume diffusion activation energy Q V we find Q GB ≈ 0.7Q V . Such a relationship is typical of metallic systems for vacancy-type diffusion (Kaur et al, 1995).…”

“…2) obtained from C(t) dependences processing also proved to be quite reasonable. For strontium-doped LaMnO 3 -based perovskites, experimental oxygen volume diffusion coefficients are available in the literature for higher temperatures (Carter et al 1992;De Souza et al 2000;Fishman et al, 2003;Routbort et al, 1997). Strontium was not found to have any profound effect on the volume diffusion coefficients of tracer oxygen atoms (Fishman et al, 2003).…”

Matrix Development for Water Vapor Resistant SiC-Based Ceramic Matrix Composites

“…The 18 O2 exchanges with 16 O in the lattice of the material as expressed by the overall reaction in Equation (5.1). 136,137 .…”

“…Under the experimental conditions used for the 18 O exchange, the diffusion equation is solved for transport in a semi-infinite medium while the boundary conditions are chosen to describe transfer of 18 O across the gas/solid interface 136,137 . The assumption is made that the diffusion rate is proportional to the difference between the 18 O concentration in the gas and the 18 O concentration at the surface at any time.…”

“…In tracer diffusion experiments, short circuit diffusion occurs in addition to bulk diffusion which is significantly slower. Short circuit 111 diffusion can be recognized by a long "tail" in the diffusion profile which extends to considerable distances in the specimen 137 . Since polycrystalline materials contain grains with random orientations and short circuit diffusion pathways the oxygen diffusion coefficient is often higher than it is for a single crystal of the same material.…”