Structure, spectroscopic investigations and discussion on conductivity of rare-earth metal thiophosphates(V) hosting silver ions in the Ag3RE[PS4]2 series (RE = Y, Dy, Ho and Er)

As the ongoing research in cation-conductive thiophosphates attracted attention especially for the Li+-ion conducting materials, their great structural variety and potential application motivated research on other thiophosphates as well. Here we present the silver-containing yttrium thiophosphate(V) Ag3Y[PS4]2 (a = 1697.65(9), b = 924.38(5), c = 937.46(5) pm, & beta; = 123.217(3)degrees, Z = 4) plus three new lanthanoid representatives, namely Ag3Dy[PS4]2, Ag3Ho[PS4]2 and Ag3Er[PS4]2, crystallizing isotypically in the monoclinic space group C2/c. These new compounds were synthesized from the respective sulfides (Ag2S, RE2S3 and P2S5; RE = Y, Dy, Ho and Er) in fused glassy silica ampoules under inert conditions at 700 degrees C. The crystal structure of the materials was revisited to reveal [AgS4]7-, [RES8]13-and [PS4]3- polyhedra as building blocks, and spectroscopic studies were first performed on these particular Ag3RE[PS4]2 samples. Electrochemical impedance spectroscopy (EIS) shed light on the Ag+-conducting potential of these thiophosphates for the example of Ag3Ho[PS4]2. Raman-spectroscopic investigations confirmed the presence of [AgS4]7- and discrete [PS4]3- tetrahedra and the studies of the diffuse reflectance (DRS) revealed optical band gaps of Eg = 2.4-2.7 eV.

Automated summary

This research investigates the cation-conductive thiophosphates and discovers several new compounds, studying their crystal structures and optical properties.