Na6Ge2S6O-ionic conductor: Synthesis, structure and ionic transportation.

White opaque single crystals of Na 6 Ge 2 S 6 O were obtained serendipitously during the preparation of Na 4 GeS 4. Then, pure glass and ceramic Na 6 Ge 2 S 6 O samples were synthesized from Na 2 S, GeS 2 , and GeO 2 reagents. The crystal structure was determined from powder and single crystal X-ray diffraction data. The physical properties were characterized by TG-DTA, SEM-EDX, Raman spectroscopy and electrochemical impedance spectroscopy. Na 6 Ge 2 S 6 O crystallizes with a new type of structure in the non-centro-symmetric space group P 2 1 2 1 2 1 , a = 6.96882 (6) Å, b = 7.04159 (6) Å, c = 26.7069 (2) Å, V = 1310.55 (2) Å3 and Z = 4. The asymmetric unit is built up of six Na+ cations surrounding a bi-tetrahedral complex anion, [S 3 GeOGeS 3 ]6−, which adopts a staggered conformation. The strongly distorted sodium polyhedra share edges and/or faces. The electrical conductivities of Na 6 Ge 2 S 6 O glass and ceramic at 25 °C are 2.9 × 10−5 S cm−1 (E a = 0.47 eV) and 1.8 × 10−7 S cm−1 (E a = 0.43 eV), respectively. [Display omitted] • The ternary system Na 2 S-GeO 2 -GeS 2 was investigated by solid state synthesis. • Glass and ceramic forms of the new Na 6 Ge 2 S 6 O compound were prepared. • Single crystals of Na 6 Ge 2 S 6 O were isolated after melting the Na 4 GeS 4 composition. • The new crystal structure was solved from powder and single crystal XRD data. • The electrical conductivity of amorphous Na 6 Ge 2 S 6 O is 2.9 × 10−5 S cm−1 at 25 °C. [ABSTRACT FROM AUTHOR]