Diffusion of Ni2+ in High-Purity MgO at High Temperatures

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Abstract
Electron microbeam probe spectroscopy has been used to determine diffusion coefficients for Ni2+ in moderate- and high-purity MgO single crystals in an argon atmosphere over a temperature range of 1900–2460°C. Samples were encapsulated in pressed cylinders of MgO powder for protection against contamination and volatilization of both solute and host crystal. No study of mass transport in MgO had previously been extended to temperatures greater than 0.66 TM. The present measurements extend to 0.88 TM but fail to reveal a change in transport mechanism. An activation energy of 2.10 eV and D0 of 1.80 × 10−5 cm2/sec, previously obtained from measurements between 1000 and 1850°C, adequately describe the present results. No significant difference in transport rates was noted between the two grades of crystals employed despite notably different dislocation densities and impurity contents.

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