Structures and ionic conductivities of the (100 - x)Na3PS4 center dot xNaI(0 <= x (mol%) <= 33) glasses and glass-ceramics were investigated. In the XRD patterns, halo patterns were observed in the composition range of 0 <= x <= 29. The glass-ceramics were prepared by a heat treatment of the glasses. In the glass-ceramics with NaI, an unknown phase which has not been reported was mainly precipitated. The Raman spectra of the glasses and glass-ceramics indicated that all samples included the PS43- units. The conductivities of glasses increased with increasing the NaI content, and the 71Na(3)PS4 center dot 29NaI glass showed the highest conductivity of 1.4 x 10(-5) S cm(-1). The conductivities of the glass-ceramics at all composition were over 10(-4) S cm(-1). (C) 2014 Elsevier B.V. All rights reserved.