Structure and vibrational study of a new material Rb0.78(NH4)0.22H(SO4)0.9(SeO4)0.1

Solid solution investigations in Rb-0.78(NH4)(0.22)(HSO4)(0.9)(HSeO4)(0.1), were carried out as part of an ongoing effort to elucidate the relationship between proton conduction, hydrogen bonding, and phase transitions. Single crystal X-ray analysis reveal that the mixed compound crystallises in the monoclinic space group C-m. The mixed compound exhibits a chain based-structure. The cations Rb+ and NH4+ are intercalated between chains formed of (HSO4-/HSeO4-) linked with O-H ... O hydrogen disordered or ordered bonds. The structure of rubidium-ammonium hydrogen sulphate-selenate is characterised by a three-dimensional N-H ... O hydrogen-bonding network connecting anionic entities (HSO4-) and (HSeO4-) to (NH4+) and participating in the stability of the material. Broader peaks in the IR and Raman spectra support the assumption of great structural disorder in this compound. Differential scanning calorimetry traces show two anomalies at 323 and 413 K characterising the two phase transitions in this material. (C) 1999 Elsevier Science B.V. All rights reserved.