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Diffusion of 51 Cr in Surface Layers of Magnesia, Alumina, and Spinel
Author(s) -
STUBICAN V. S.,
HUZINEC G.,
DAMJANOVIĆ D.
Publication year - 1985
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1985.tb15294.x
Subject(s) - diffusion , ionic bonding , enthalpy , arrhenius equation , surface diffusion , chemistry , activation energy , thermal diffusivity , grain boundary diffusion coefficient , analytical chemistry (journal) , spinel , materials science , thermodynamics , crystallography , ion , adsorption , grain boundary , metallurgy , physics , microstructure , organic chemistry , chromatography
Diffusion of 51 Cr isotope on MgO (100), Al 2 O 3 (0001, and MgAl 2 O 4 (111) surfaces was investigated by using the edgesource method. The surface diffusion parameter, αD,δ, where α is the segregation factor, D , the surface diffusion coefficient, and δ the thickness of the high‐diffusivity layer, was determined for the temperature region 650° to 1250°C. For calculation of experimental results Whipple's solution was used. Arrhenius plots show a break at ∼1050°C for MgO and at ∼900°C for MgAl 2 O 4 . Above these temperatures vapor transport seems to be the overriding diffusion mechanism. Below these temperatures ionic transport predominates. Ionic transport is the predominant mechanism for surface diffusion of 51 Cr on Al 2 0 3 over the entire investigated temperature region. This can be explained by the weak bond between Cr‐vapor species and Al 2 0 3 surface. The apparent activation energies for ionic transport of 51Cr are 110 ± 12, 121 ± 12, and 119 ± 12 kJ/mol on MgO, Al 2 O 3 , and MgAl 2 O 4 surfaces, respectively. They include enthalpy of motion and binding enthalpy and are 2.5 to 2.8 times smaller than the activation energies for volume diffusion. Investigations of surfaces by LEED, Auger, and SIMS indicated structural nonperiodicity and surface segregation of impurities.