Structure of alkali tellurite glasses from neutron diffraction and molecular orbital calculations

Abstract

The structure of pure TeO 2 and alkali tellurite glasses has been examined by neutron diffraction and ab initio molecular orbital methods. The experimental radial distribution functions along with the calculated results have demonstrated that the basic structural units in tellurite glasses change from highly strained TeO 4 trigonal bipyramids to more regular TeO 3 trigonal pyramids with increasing alkali content. It has also been shown that the TeO 3 trigonal pyramids do not exist in the form of isolated units in the glass network but interact with each other to form intertrigonal Te¯O linkages. The present results suggest that nonbridging oxygen ͑NBO͒ atoms in tellurite glasses do not exist in their ''pure'' form; that is, all the NBO atoms in TeO 3 trigonal bipyramids will interact with the first-and/or second-neighbor Te atoms, resulting in the three-dimensional continuous random network even in tellurite glasses with over 30 mol % of alkali oxides.

Alkali environments in tellurite glasses

“…Molecular orbital calculations have also been performed for cluster models of sodium tellurite glasses [4] and Na-O coordinations of 3, 4 and 5 were found. It was concluded that the 5-coordinated environment is more representative of the glass, based on the results of the previous 23 Na NMR study [11].…”

“…The local structure of alkali M2O-TeO2 glasses (M = Li, Na, and K) has been studied extensively using neutron diffraction [1][2][3][4][5], X-ray diffraction [6,7], EXAFS [7,8], Raman scattering [7,9,10], NMR [2,[11][12][13] and RMC modelling [2,14]. In these studies, particular emphasis was placed on determining the local environment of tellurium and there is a general consensus that the average tellurium coordination number, nTeO, decreases as an oxide modifier is added to the glass network, the change being driven by the bonding requirements of the modifier.…”

Structural investigations of the xTeO2–(1−x)GeO2 (x=0, 0.2, 0.4, 0.6, 0.8 and 1) tellurite glasses: A composition dependent Raman spectroscopic study

“…Currently, there exist a large amount of literature regarding the structure of pure TeO 2 and xM 2 O-(1-x)TeO 2 (M 2 O: alkali oxide, x: mole fraction) glasses with a variety of techniques such as X-ray diffraction [6][7][8], neutron diffraction [8,9], NMR [10][11][12], Mösbauer spectroscopy [13], EXAFS [14], ab initio quantum-mechanical calculations [15,16], molecular orbital calculations [9], Brillouin [17], IR [ 18,19] and Raman scattering [20][21][22][23]. However, a limited number of papers have been focused on binary glassy systems where both components are glassformers participating directly in the formation of the vitreous network.…”

Preparation of Organic-Inorganic Hybrid Precursors O = P (OSiMe3)x(OH)3-x for Low-Melting Glasses.

“…We have reported or ganicinorganic hybrid lowmelting glasses prepared from a nonaqueous acidbase reaction in our previous papers. 1)3) The hybrid glass precursor consisting of Si(Me) 2 OP framework was prepared through a nonaqueous acidbase polycondensation reaction of POH{SiCl¨POSi{ HClª from the mixtures of orthophosphoric acid H 3 PO 4 and dialkyldichlorosilane R 2 SiCl 2 . 1) Based on this reaction, we prepared organicinorganic hybrid lowmelting glasses SnOMe 2 SiOP 2 O 5 , 2) of which T g 's were ranging from |25 to 50 C. Detailed structure of the glasses was also examined by 29 Si MAS NMR spectroscopy and ab initio molecular or bital (MO) calculations.…”