LI+ DIFFUSION IN THE FAST IONIC CONDUCTOR LI3N INVESTIGATED BY BETA-RADIATION DETECTED NMR

Applying the method of beta-radiation detected nuclear magnetic resonance/relaxation (beta-NMR) to Li-8 nuclei in (Li3N)Li-7 single crystals comprehensive information on static and dynamic properties was obtained. Below T congruent-to 200 K the electric field gradients (EFG) at the two inequivalent Li lattice sites (Li(1), Li(2)) were determined. The spin-lattice relaxation (SLR) behaviour above T congruent-to 300 K and the Li-8 NMR signals in the extreme narrowing regime (T greater-than-or-equal-to 500 K) could be attributed to interlayer diffusion involving Li+ jumps between Li(1) and Li(2) lattice sites ((1 <-> 2) jumps). In thc temperature range 200 K less-than-or-equal-to T less-than-or-equal-to 300 K the transients of the Li-8(1) and Li-8(2) polarizations were measured separately by applying a special radiofrequency scheme. The different SLR behaviour allowed us to study the Li+ intralayer diffusion confined to the Li2N layers. Furthermore, ultra-slow interlayer (1 <-> 2) jumps with correlation times of up to 10 s were observed in this T region. Below 200 K a non-exponential Li-8 polarization decay depending weakly on B and T was observed. The SLR in this T range is discussed in terms of statistically distributed relaxation centres.