THE LITHIUM-SODIUM-METHYLAMINE SYSTEM - DOES A LOW-MELTING SODIDE BECOME A LIQUID-METAL

The properties of the simplest sodide, LiNa(CH3NH2)(n), are reported a s a function of n. The phase diagram, established by using differentia l thermal analysis, shows the presence of a compound with n approximat e to 6, which melts congruently at 168.5 +/- 0.5 K. Two eutectics are present with n = 7.3 +/- 0.3, T-1 = 166 +/- 1 K and n = 3.0 +/- 0.2, T -2 = 151 +/- 1 K. The phase diagram was extended to metal concentratio ns that correspond to n = 1.45 and indicated the presence of a second compound with 2 less than or equal to n less than or equal to 3. The p roperties of these systems were investigated by EPR and alkali metal N MR spectroscopies and static magnetic susceptibilities. The Na-23 NMR results clearly show that sodium is present as Na- for n greater than or equal to 8. At higher metal concentrations the resonance line shift s smoothly toward more paramagnetic values (positive), with larger shi fts at higher temperatures. EPR spectroscopy shows a transition from a single nearly symmetric line at large values of n to a strongly asymm etric signal characteristic of conduction electron spin resonance (CES R) when n less than or equal to 5. The line shapes were fit by theoret ical expressions and showed that liquid LiNa(CH3NH2)(4) has a conducti vity comparable to that of liquid Li(CH3NH2)(4), a near metal.