Phase equilibria, high conductivity ambient temperature liquids, and glasses in the pseudo-halide systems AlCl₃-MSCN (M = Li, Na, K)

In the family of pseudo binaries, xAlCl₃-(1 - x)MSCN (M = Li, Na, or K), ambient-temperature molten salt solutions are formed over the composition range, 0.35 < x < 0.75. These molten salt solutions readily form glasses. A partial determination of the phase equilibria for these pseudo binaries was made. For all three AlCl₃-MSCN systems, a eutectic occurs at ∼65 mol % AICl₃ and at 50, 55, and 70°C, for M = Li, Na, and K, respectively, in striking resemblance to the corresponding MCI-AICl₃ systems. The decoupling of conductivity from viscosity is very pronounced amounting to almost 9 orders of magnitude for LiAlCl₃SCN at T_g, and more for the Na case. The highest room temperature conductivity observed was ∼10^-3(Ω - cm)^-1 for M = Li and x = 0.6. Upon adding ∼24 mole % LiAlC₄, the conductivity increases to values of log (σ/(Ω - cm) ¹) = - 3.9, - 2.3 and - 1.0 at 0°C, 25°C and 100°C, respectively. With little change of conductivity, the eutectic compositions assume a gel-like consistency after long periods at room temperature, apparently due to homogeneously nucleated, possibly metastable, crystalline phases.