X-ray Crystal Structure Analysis of Sodium-Ion Conductivity in 94Na3PS4•6Na4SiS4 Glass-Ceramic Electrolytes

Rietveld analysis of cubic Na3PS4 in the 94Na(3)PS(4)center dot 6Na(4)SiS(4) (mol%) glass ceramic indicates that two Na+ sites (Na1 and Na2) can be found in cubic Na3PS4 and that the phosphorus atoms in cubic Na3PS4 are partially replaced by silicon in the 94Na(3)PS(4)center dot 6Na(4)SiS(4) glass ceramic. The electron-density distribution of the cubic Na3PS4 structure, obtained by the maximumentropy method/Rietveld method, revealed that cubic Na3PS4 contains three-dimensional Na+ conduction pathways along the Na1 and Na2 sites. From the Rietveld analysis, the cubic Na3PS4 in the 94Na(3)PS(4)center dot 6Na(4)SiS(4) glass ceramic has a larger siteoccupancy of Na2 than that in the Na3PS4 glass ceramic, which may be responsible for the improvement in Na+ conductivity.