Composite samples were prepared by thermal decomposition of precursors at 400C, or by conventional mixing. It was shown that, regardless of the preparation technique, if the grain size of the alumina in the composites was sufficiently small (tens of nm) then, after prolonged heating, the heterogeneous system reached a metastable thermodynamic state; giving a nano-composite in which the sulfate was present in an unusual epitaxial state. Stabilization of this state was caused by a strong interface interaction which led to the formation of an intermediate thin layer of lithium aluminate that glued the sulfate and alumina phases together and provided contact. The ionic conductivity of the sulfate in the composites changed smoothly at the phase transition, and the activation energies were equal to 0.40 and 0.66eV for temperatures which were above 470C and below 280C, respectively.

N.F.Uvarov, B.B.Bokhonov, V.P.Isupov, E.F.Hairetdinov: Solid State Ionics, 1994, 74[1-2], 15-27