Abstract
Ternary alkali metal thiobismuthates A(9)Bi(13)S(24) (A = K, Rb) were synthesized by direct combination reactions at 650 degrees C. The compounds crystallize in the monoclinic space group C2/m (no. 12) with cell parameters a = 30.919(1) angstrom, b = 4.1008(2) angstrom, c = 20.9072(9) angstrom, beta = 105.826(3)degrees for K9Bi13S24 (1) and a = 31.823(6) angstrom, b = 4.1177(8) angstrom, c = 21.086(4) angstrom, beta = 105.62(3)degrees for Rb9Bi13S24 (2). The crystal structure of 1 contains a 3D [K2Bi13S24](7-)polyanionic frame-work, whereas 2 consists of 2D [RbBi13S24](8-) polyanionic slabs stacked along [201]. Both 1 and 2 are semiconductors with a band gap of 1.4 and 1.3 eV, respectively, which is supported by an electronic structure calculation. 1 melts congruently at 580 degrees C, while 2 melts incongruently at 575 degrees C. 1 and 2 are airstable and insoluble in water and organic solvents.