Characterization and structure determination of disordered rubidium ammonium sulfate tellurate Rb1.12(NH4)0.88SO4.Te(OH)6

L. Ktari, M. Dammak*, T. Mhiri, A. W. Kolsi

Laboratoire de lĺEtat Solide, FacultÚ des Sciences Sfax, B. P.802, 3018 Sfax, Tunisia

* Corresponding author. E-mail : meddammak@yahoo.fr

Received : 12 February 2002; revised version accepted :07 June 2002

Abstract

The rubidium ammonium sulfate tellurate salt has been prepared using the reaction of the rubidium sulfate, ammonium sulfate and telluric acid. The solid solution of Rb1.12(NH4)0.88SO4.Te(OH)6 (RNST) is characterized by Raman, IR spectra and DSC analysis. The RNST crystal is monoclinic structure with P21/a space group. The parameters are: a= 11.438(5)┼, b= 6.643(4)┼, c= 13.700(4)┼, b = 106.896(2)░ and Z= 4. The structure is refined by least-squares methods to R= 2.8 % for 1620 reflections. The main result is the presence of two different and independent anionic groups (TeO and SO) in the same crystal. Differential scanning calorimetry traces show one anomaly at 418K, two epaulments at 483 and 510K corresponding to three phase transitions and one strong peak at 517K dealing with the decomposition of the salt. Raman and IR spectra of RNST material, recorded at room temperature performed between 10 and 4000 cm-1, show that anionic groups coexist independently in the same crystal.

Keywords: Sulfate tellurate; Rubidium compound; Structure; DSC.

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