Eur. Phys. J. AP
Volume 11, Number 2, August 2000
|Page(s)||83 - 89|
|Published online||15 August 2000|
Contribution to the theoretical and experimental study of the dielectric material Rb0.7(NH4)0.3HSO4
Groupe diélectrique de Sfax, Faculté des Science de
Sfax, BP 763, 3000 Sfax, Tunisia
2 Département de Physique, Institut Préparatoire Aux Etudes d'Ingénieurs de Sfax, BP 805, 3000 Sfax, Tunisia
3 Département de Chimie, Faculté des Sciences de Sfax, BP 763, 3000 Sfax, Tunisia
Corresponding author: email@example.com
Revised: 3 May 2000
Accepted: 26 May 2000
Published online: 15 August 2000
The mixed sulphate acid Rb0.7(NH4)0.3HSO4 presents at room temperature a phase with a structure similar to the one of the parent compounds RbHSO4 and NH4HSO4. Different techniques of the study of phase transitions show that this compound exhibits five phases with varying temperature and in particular the appearance of a new phase (noted IV) in comparison of the phase diagram of parent compounds, this phase takes place in the range of temperature T between 330 and 435 K. The symmetry of the mixed compound at room temperature (phase III) has been performed again by X-ray diffraction on single crystals. The crystallographic characterization of the phase IV is made by X-ray diffraction on powder sample. Crystallographic parameters in this phase are then obtained whereas group theory considerations gives the most probable space group of this phase. In this work, the phase transitions are studied by dielectric measurements. Theoretical study of the behaviour of dielectric susceptibility based on LANDAU theory of phase transitions shows an improper ferroic character of the transition occurring at 330 K with a faintness index f equal to 2.
PACS: 61.50.Ah – Theory of crystal structure, crystal symmetry; calculations and modeling / 61.50.Ks – Crystallographic aspects of phase transformations; pressure effects / 33.20.Rm – X-ray spectra
© EDP Sciences, 2000
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