LAUSR

Abstract During the search for selenium analogues of FeTe 2 O 5 Cl, the new iron (III) tellurate(IV) selenate(IV) chloride with the composition Fe[(Te 1.5 Se 0.5 )O 5 ]Cl was synthesized by chemical vapor transport (CVT) reaction and characterized by TGA-, EDX-,SCXRD-analysis, as well as IR and Raman spectroscopy. It was found that Fe[(Te 1.5 Se 0.5 )O 5 ]Cl crystallizes in the monoclinic space group P 2 1 / c with unitcell parameters a  = 5.183(3) A, b  = 15.521(9) A, c  = 7.128(5) A and β = 107.16(1)°. The crystal structure of Fe[(Te 1.5 Se 0.5 )O 5 ]Cl represents a new structure type and contains electroneutral heteropolyhedral layers formed by dimers of the [FeO 5 Cl] 8– octahedra, linked via common O-O edges, and mixed [Te 3 SeO 10 ] 4- tetramers. Adjacent layers are stacked along the b axis and linked by weak residual bonds. The new compound is stable up to 420 °C. DFT calculations predict Fe[(Te 1.5 Se 0.5 )O 5 ]Cl to be a wide-gap semiconductor with the band gap of ca. 2.7 eV.