Abstract: The present invention relates to the preparation of materials and finds one application in the preparation of ion conductors and precursors therefor.There is disclosed a process for use in the preparation of a material of the general formulaNa.sub.1+x Zr.sub.2 Si.sub.x P.sub.3-x O.sub.12which includes the step of preparing a precursor for the material by forming a precipitate containing zirconia (or a precursor therefor) and at least some of the other elements appropriate to the material.For materials with the highest conductivities for applications as solid electrolytes with low resistance x preferably takes a value in the range: 1.8.ltoreq.x.ltoreq.2.2.