Diffusion of Transition Metal Ions in Single-Crystal MgO

Abstract

Diffusion coefficients for transition metal ions in single-crystal MgO have been determined in the temperature range 1000°-1850°C. from concentration distributions obtained with the aid of x-ray absorption analysis and electron microbeam probe spectroscopy. The variation of the diffusion coefficients with temperature yields D0 = 8.83 (10)-5, 5.78 (10)-5, and 1.80 (10)-5 cm2/sec and activation energies for diffusion of 1.81, 2.06 and 2.10 electron volts for Fe2+, Co2+, and Ni2+, respectively. It is found that the activation energy for diffusion increases exponentially with the ratio ionic radius/ionic electronic polarizability for the diffusing cation and that D0 increases exponentially with the cation radius cubed. This correlation suggests that the diffusion mechanism for all three ions is the same and that self-diffusion in MgO takes place via the same process.

Prediction of Site Preference of Implanted Transition Metal Dopants in Rock-salt Oxides

“…As charge states of substitution doped Fe do not match with experimental observation, hence Fe atoms most likely occupy interstitial sites in MgO [1]. Also, if Fe does not occupy interstitial position, it will not migrate out of MgO to form metallic precipitate as shown in some experiments [80,90].…”

Diffusion in Oxides

“…Co. Cobalt diffusion in periclase at low concentrations was investigated by Wuensch and Vasilos (1962) at 1000-1810 °C, using diffusion couples consisting of a thin layer of oxide sandwiched between two nominally pure MgO single crystals. Diffusion profiles in the quenched A l; W h it n e y & S tu b ic a n , 1 9 7 1 b A l; V a n O r m a n e t a l. , 2 0 0 9 samples were measured using an electron microprobe.…”

On the Interpretation of Lattice Diffusion in Magnesium Oxide

“…Concentration as a (34,37) of hosc crystal 2848(17)* Co(34), Fe 46Sc(31), 115Cd (27) jC(x,t)dx -S Mn (37). 91 (38).…”