Structural peculiarities and Raman spectra of TeO 2 /WO 3 -based glasses: A fresh look at the problem Andreı ¨ Mirgorodsky a , Maggy Colas a , Mikhael Smirnov b , The ´r  ese Merle-Me ´ jean a , Raouf El-Mallawany c,1 , Philippe Thomas a,n a Laboratoire Science des Proce´de ´s Ce´ramiques et de Traitements de Surface, UMR 6638 CNRS, Centre Europe´en de la Ce´ramique, 12 rue Atlantis, 87068 Limoges Cedex, France b Fock Institute of Physics, Saint-Petersburg State University, 1 Ulyanovskaya street, 198504, Petrodvorets, Saint-Petersburg, Russia c Physics Department, Science College, Northern Borders University, Kingdom of Saudi Arabia article info Article history: Received 30 August 2011 Received in revised form 5 January 2012 Accepted 6 February 2012 Available online 10 February 2012 Keywords: Tellurite glasses Raman spectroscopy Vibrational analysis Phase separation abstract Ideas currently dominating the field of structural studies of TeO 2 -based glasses are critically considered. A new physically and chemically consistent approach to the constitution of binary TeO 2 –WO 3 glasses is proposed, in which the reasoning coming from the Raman spectra reexamination are correlated with the basic principles of thermodynamics. Separation into two phases is suggested in such glasses. One phase is TeO 2 , and another is Te(WO 4 ) 2 consisting of tetrahedral [WO 4 ] 2 anions and of Te 4 þ cations. Supplementary M n O k oxides added to the glasses are found incorporated in the former phase, thus producing solid solutions (for M¼Ti, Nb) or tellurite compounds (for M¼Nd). & 2012 Elsevier Inc. All rights reserved. 1. Introduction The objective of the present work was to study the structural changes and related effects in binary TeO 2 –WO 3 glasses when adding to them small amounts of modifiers Y k O l (Y ¼ Ti, Nb, Nd). The compounds thus obtained were multi-component TeO 2 - based glasses which generally manifest extraordinary dielectric characteristics currently regarded as very promising for nonlinear optical engineering [1]. Their nature is a challenge for the modern solid state physics and chemistry, and this is the factor determin- ing an increasing number of the relevant investigations mainly aimed at understanding the structural particularities of those glasses (see e.g., Ref. [2]). Very often, the key to understanding the principles of atomic arrangement and chemical constitution of the glasses are the diffraction technique or vibrational spectroscopy data on the crystalline compounds resulting from the glass crystallization [3]. Unfortunately, the latter is not the case of TeO 2 –WO 3 glasses. On the one hand, none of them crystallizes in a particular lattice [4], and, on the other hand, the crystal chemistry aspects of both the initial compounds, TeO 2 and WO 3 , are far from the final clarity, which makes the speculations about structural features of TeO 2 –WO 3 glasses a very delicate problem. At first glance, the above circumstances seem to be responsible for the fact that despite many years of researches and the bulk of related communications, the question of the atomic arrangement of those glasses remains the open and confused question. However, a closer examination of the present state of affairs leads us to recognize that such a situation is not somewhat intrinsic exclusively in the TeO 2 –WO 3 compounds, but reflects the general state of those methodological and ideological doctrines which are presently domi- nant in the field of structural investigations of TeO 2 -based glasses, and which, we venture the opinion, are largely fallacious. After reading a number of relevant publications (they are legion), there is the impression that most of their authors have as peculiar notions of the complex oxide glass formation as if the thermodynamic and fundamental chemical laws are not valid for processes producing those glasses. In particular, the point that these processes would result in quite distinctive chemical compounds, namely, the oxide salts, is beyond considerations, and the complex anions necessarily representing the basic structural fragments of the salts, i.e., of the glasses under study, are never discussed and even mentioned. Instead of this, hazy notions of certain atomic ‘‘groups’’ or ‘‘units’’ lacking any objective sense are universally used. The existence of such species is customarily asserted without any argumentation, just announcing ‘‘it is well known that y.’’ Their chemical nature and genesis are never considered, so that nothing straitens to proclaim extravagant ideas of their atomic structures Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jssc Journal of Solid State Chemistry 0022-4596/$ - see front matter & 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.jssc.2012.02.011 n Corresponding author. Fax: þ33587502304. E-mail address: philippe.thomas@unilim.fr (P. Thomas). 1 Permanent Address: Physics Dept., Faculty of Science, Menofia University, EGYPT. Journal of Solid State Chemistry 190 (2012) 45–51