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Raman characterization of Pb2Na1−xLaxNb5−xFexO15 and Pb0.5(5−x)LaxNb5−xFexO15 (0≤x≤1) solid solutions |
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| Authors: | M Bouziane M TaibiL Saviot A Boukhari |
| Institution: | a Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Avenue Ibn Batouta, BP 1014 Rabat, Maroc b Laboratoire de Physico-Chimie des Matériaux, LAF 502, Ecole Normale Supérieure, BP 5118, Rabat, Maroc c Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 5209 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47 870, F-21078 DIJON Cedex, France |
| Abstract: | The ferroelectric compounds Pb2Na1−xLaxNb5−xFexO15 and Pb0.5(5−x)LaxNb5−xFexO15 (0≤x≤1) with the tungsten bronze type structure have been investigated using Raman spectroscopy. The evolution of the spectra as a function of composition at room temperature is reported. In the frequency range 200-1000 cm−1 three main A1 phonons around 240 (υ1), 630 (υ2) and 816 (υ3) cm−1 were observed. The broadening of the Raman lines for high values of x originates from a significant structural disorder. This is in good agreement with the relaxor character of these compositions. The lowest-frequency part of the spectra, below 180 cm−1, reveals a structural change in the studied solid solutions. The behaviour of the Raman shift of the υ1 mode confirms that in Pb2Na1−xLaxNb5−xFexO15, a clear anomaly occurs in the vicinity of x=0.4. |
| Keywords: | Tungsten bronze Raman scattering Relaxor behaviour Structural change |
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