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A unified model of ionic motion in glasses is presented which relates consistently the different quantities observed in nuclear-spin relaxation and electrical-conductivity relaxation due to thermally activated ionic diffusion. Corresponding experimental data obtained in a low-ionic-conductivity fluorozirconate glass are shown to be in reasonable agreement with the present approach. Limitations of the model are pointed out and are discussed in view of observed deviations between the different experimental results.

The reorientational motion of the tetrahydrofuran guest molecule in the clathrate hydrate C4H8O · 17D2O was studied by proton NMR spin‐lattice relaxation measurements in the temperature range 4 — 278 K. The results are interpreted by a Davidson‐Cole distribution of correlation times with a distribution parameter ß = 0.12. The maximum or cutoff time τ0 in this distribution obeys an activation law with prefactor 3.75 · 10−13 s and activation energy 4140 J mol−1. At temperatures below 20 K the motion of the guest molecules can be described by a coupled ensemble of quantummechanical hindered rotators where the reorientation rate is again described by a Davidson‐Cole distribution.

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We have determined NMR linewidths and nuclear spin relaxation rates for F, Li, and Na nuclei, and electrical conductivity in ZrF 4-based fluoride glasses as a function of temperature. The results indicate that both Li and F are mobile in the glass containing 20 mole% LiF, whereas only F is mobile in glasses containing NaF (up to 30 mole%) or no alkali ions. Finally we compare and discuss the activation energies for the various parameters. RESUME Des mesures de conductivité électrique et de RMN de F, Li et Na ont e'te' re'alise'es sur des verres fluorures à base de ZrF 4 : les variations des largeurs de raies de résonance et des temps de relaxation ont été e'tudie'es en fonction de la température. Les résultats démontrent que les ions Li et F sont mobiles dans le verre contenant 20% de LiF(en fraction molaire). Dans le cas des verres contenant du NaF (jusqu'à 30% en mole) ou ne contenant pas de cation alcalin, seul l'ion F est mobile. Les e'nergies d'activation déduites des divers paramétres sont comparées et analysées.