Bensaid H.,Solid State Materials Laboratory |
Bih L.,Materials Science Group |
Manoun B.,Materials Science Group |
Azrour M.,Materials Science Group |
And 2 more authors.
Journal of Molecular Structure | Year: 2011
Crystal structures of Ba2.15-xNa0.7+ xNb5-xWxO15 (BaNaNbW) materials were investigated by X-ray diffraction and refined using the Rietveld method. It is shown that all the samples crystallize in the tungsten tetragonal bronze (TTB) like structure and form a solid solution in the range (0 ≤ x ≤ 1). To study the temperature induced phase transition in these compounds, Raman spectra were collected in situ at room pressure and elevated temperatures, up to 330°. The Raman results show strong evidence that the materials under study go through a phase transition around Te = 270 °C. The value of the transition temperature depends on the chemical composition and increases with increasing tungsten content in the materials at a linear rate. The observation of this phase transition by Raman technique is in agreement with dielectric spectroscopy anomaly. © 2010 Elsevier B.V. All rights reserved.