Glass-ceramics of the titanium-, germanium- or tellurium-containing Na5RSi4O12-type (R = rare earth; Y) Na+-superionic conductors (N5YXS) were prepared by crystallization of glasses with the composition Na3+3xY1 - xXySi3 - (Y) O-9 (X = Ti; NYTiS, Ge; NYGeS, X = Te: NYTeS), and the effects of X elements on the separation of the phase and the microstructural effects on the conduction properties of glass-ceramics were discussed. The combination of x and y was most varied in N5YGeS and more limited in the order of N5YTeS>N5YTiS. Their conductivities and an activation energies are of the order of 10(-2) S/cm at 300 degrees C and of 15 to 24 kJ/mol, respectively. The conductivity of the glass-ceramic N5YXS decreases giving the order N5YGeS>N5YTeS>N5YTiS. It is considered that this order corresponds to the N5 single phase region. Large enhancement of electrical conductivity was observed in the glassceramics as the grain growth was promoted with increase of heating temperature and heating time for crystallization. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.