Abstract

L. Loubbidi*¹, M. Naji², B. Orayech³, A. Chagraoui¹, J. M. Igartua⁴, A. Moussaoui¹ and  A. Tairi¹

DOI : http://dx.doi.org/10.13005/ojc/320105

Thanks to its peculiar structural properties, the high temperature δ-phase of Bi₂O₃ is considered as the best oxide ion conductor. Many efforts to stabilize this structure at room temperature have been deployed. In the present study, we have successfully stabilized the δ-phase by chemically introducing tetra- Te⁴⁺ and pentavalent Ta⁵⁺ cations into the structure. A series of compounds with different percentage of Te⁴⁺/ Ta⁵⁺ were obtained. Their structural and vibrational properties were investigated. From the Rietveld refinement of X Ray diffraction pattern we show that the composition x = 0.2 crystallizes in the cubic symmetry, space group Fmm (ITA No. 225) with a lattice parameter a =5.49 Å. The reliability factors are: R_F =2.151 % and R_Bragg=2.545 % confirm the goodness of the refinement. From the evolution of Raman bands, we confirm the existence of the solid solution features. Furthermore, comparing the spectra of δ-Bi₂O₃ with the alpha phase, we comfortably suggest that the decrease of the number of Raman bands is a consequence of an increase in the lattice symmetry. Similarly to other fluorite compounds, we show that the structure presents oxygen defects clearly identified in the Raman spectra.

Bi2O3; Ta2O5; TeO2; X-Ray diffraction; Raman spectroscopy;Bi2O3

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