Solid solutions of the composition LixAl12-3xSi2xN12 (1less than or equal toxless than or equal to3) have been prepared via a precursor route. According to XRD studies all phases obtained have wurtzite-type substructures with an orthorhombic superstructure related to LiSi2N3. However, observed powder patterns cannot be adequately described in orthorhombic symmetry, and the significant diffusiveness of the superstructure reflections indicates the presence of disorder. High resolution electron microscopy emphasizes the highly defective nature of the microstructure and the presence of nanoscale domains of apparently varying symmetry. Local ordering of metal ions and slight spatial variations of the composition are assumed to be possible reasons for the long-range inconsistencies of the structures. The Li+ ion conductivity, as measured on selected solid solutions, is lower, than that of LiSi2N3.