${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ NMRs are used to investigate the lithium ion dynamics in $\mathrm{Li}\mathrm{P}{\mathrm{O}}_3$ glass. In particular, ${}^6\mathrm{Li}$ NMR stimulated-echo experiments are used to provide straightforward access to two-time correlation functions characterizing the lithium ionic hopping motion in the millisecond regime in a glassy ion conductor. Temperature-dependent measurements serve to separate the spin diffusion contribution and the dynamic contribution to the stimulated-echo decays. The ${}^6\mathrm{Li}$ NMR correlation functions of $\mathrm{Li}\mathrm{P}{\mathrm{O}}_3$ glass describing the lithium ionic motion show pronounced nonexponential decays, which can be well described by a stretched exponential function with a temperature-independent small stretching parameter $\beta =0.27$, indicating the complex nature of the lithium dynamics. The temperature dependence of the mean correlation times $⟨\tau ⟩$ resulting from these stimulated-echo experiments is described by an activation energy $E_a=0.66\mathrm{eV}$. The values of $⟨\tau ⟩$ are in good agreement with time constants from previous electrical and mechanical relaxation studies. At appropriate temperatures, the ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ NMR spectra are superpositions of a broad and a narrow spectral component, which result from slow and fast lithium ions, respectively, on the NMR time scale. A detailed analysis of the temperature dependence of these line shapes provides information about the distribution of correlation times.

• Received 20 August 2007

DOI:https://doi.org/10.1103/PhysRevB.77.104301