Synthesis, Crystal Structure and High-Temperature Transport Properties of the New Cluster Compound Rb2Mo15Se19.

Abstract We report on the synthesis, crystal structure and high-temperature transport properties of Rb2Mo15Se19, a new member of the large family of M2Mo15Se19 (M=In, Tl, K, Ba) cluster compounds. Polycrystalline samples and single crystals of the ternary selenide Rb2Mo15Se19 were obtained by solid-state reactions. The trigonal crystal structure, successfully refined in space group R 3 ¯ c (No. 167) with unit-cell parameters a=9.7618(1) A, c=58.254(1) A and Z=6, was determined by single-crystal X-ray diffraction. The crystal structure contains Mo 6 Se 8 i Se 6 a and Mo 9 Se 11 i Se 6 a cluster units in equal proportion and separated from each other by large voids, which are filled up by Rb atoms. Measurements of the electrical resistivity, thermopower and thermal conductivity revealed that Rb2Mo15Se19 behaves as a p-type metal with relatively low electrical resistivity and thermopower. Despite its complex crystal structure, the lattice thermal conductivity that amounts to 1.3 W m−1 K−1 at 300 K is significantly higher than in Ag-filled analogues, which provides possible guidelines to enhance its thermoelectric properties.