STUDIES OF SELF-DIFFUSION IN POTASSIUM FLUORIDE BY NUCLEAR MAGNETIC RESONANCE TECHNIQUES

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Abstract
Nuclear rnagnetic resonance relaxation tinie measurernents of T1 and T1ρ, have been made on pure and Ca2+-doped single crystals of KF over the temperature range 470 to 1090 K. The process responsible for relaxation is self-diffusion. From the temperature dependence of T1 and T1ρ, the cation migration enthalpy is found to be 0.83eV and the anion migration enthalpy is found to be 1.35 eV. Comparison of the jurnp frequencies for potassium and fluoride ions calculated from the relaxation times and from conductivity rneasurements shows that extrinsic diffusion takes place via cation single vacancies and irnpurity-vacancy complexes. The latter contribute to the relaxation process, indicating that, in KF, free and complexed vacancies have similar diffusion rates. At higher temperatures there is a significant contribution from anion vacancies to the diffusion process

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