Structural, vibrational study and conductivity investigation of a new mixed dipotassium hydrogenselenate dihydrogenarsenate K2(HSeO4)1.5(H2AsO4)0.5

An investigation of solid solutions of KHSeO4-KH(2)ASO(4) has led to the discovery of a new compound, K-2(HSeO4)(1.5)(H2AsO4)(0.5) (dipotassium hydrogenselenate dihydrogenarsenate) (denoted KHSeAs). The crystals have been prepared at room temperature by slow evaporation of an aqueous solution containing K2CO3, H2SeO4 and H3AsO4. The compound was characterized by X-ray single-crystal analysis performed at room temperature and reveal that it crystallizes in the space group P1 (1) over bar with the following crystal data: a=7.4532(2) angstrom, b=7.7151(2) angstrom, c=7.7911(2) angstrom, alpha=71.8843(17), beta=87.7804(16)degrees and gamma=86.0475(15)degrees. The structure is characterized by HSeO4- and disordered (HxSe/As)O-4(-) tetrahedral connected to dimers via hydrogen bridges. These dimers are linked and stabilized by an additional hydrogen bonds (O-H-O) and hydrogen bonds (O-H center dot center dot center dot O) to built an anionic chains of dimers, which are parallel to the [0 1 0] direction at x=0.5. The infrared spectrum at room temperature confirms a structural disorders and the coexistence of two different anions (H2AsO4- and HSeO4-) in the same crystal structure. The thermogravimetry (TG) analysis (T.G.A) shows from 450 K two weight losses. No phase transitions were observed by the differential thermal analysis (DTA) curve below this temperature. Moreover, protonic conduction of the mixed compound determined by impedance and modulus spectroscopy has been studied in the temperature range 298-473 K. (C) 2013 Elsevier Ltd. All rights reserved.