American Journal of Applied Sciences 4 (5): 323-327, 2007 ISSN 1546-9239 © 2007 Science Publications Corresponding Author: Halimah M.K., Ultrasonic Laboratory, Department of Physics, Faculty of Science University Putra Malaysia, 43400 Serdang, Selangor, Malaysia 323 Structural Analysis of Borotellurite Glass Halimah M.K., Daud W.M., Sidek H.A.A., Zainal A.S., Zainul A.H. and Jumiah H. Ultrasonic Laboratory, Department of Physics, Faculty of Science, University Putra Malaysia 43400 Serdang, Selangor, Malaysia Abstract: The average cross-link density, number of the network bonds per unit volume, average stretching force constant, atomic ring size and the ratio K bc /K e have been calculated and discussed according to bond compression model for borotellurite glass. The result showed that the connectivity and rigidity of the borotellurite glasses increases with TeO 2 content due to the transformation of BO 3 units to BO 4 and TeO 3 units to TeO 4 . Comparison between theoretical calculated and experimental elastic moduli and Poisson’s ratio has been carried out. The results showed good agreement between experimental and theoretical calculated elastic moduli. Key words: Borotellurite glass, bond compression model INTRODUCTION Tellurite glasses with the unique physical properties and applications were reported by El- Mallawany [1] . Elastic properties are very informative about the structure of solids and are directly related to the interatomic potentials. Elastic properties also provide the information about internal arrangement of the constituent oxides and the mechanical strength of the glass. Elastic moduli of tellurite, binary transition tellurite, rare earth tellurite and multicomponent tellurite glasses including halide, hydrostatic and uniaxial pressure dependencies of ultrasonic waves in these glasses at room temperature have been measured and reported [1] . Recently, elastic properties of (TeO 2 ) 50 - (V 2 O 5 ) 50-x (TiO 2 ) x glasses using pulse-echo technique have been studied [2] . TeO 2 and B 2 O 3 are known as glass forming oxides. The structure of tellurite glass is a laminar network based on triangular TeO 3 pyramids or square TeO 4 pyramids [3] . Boron oxide B 2 O 3 in its glassy form is a laminar network consisting of boron atoms 3-fold coordinated with oxygen which can form six-membered boroxol rings (B 3 O 6 ), as reported earlier by Krogh- Moe [4] . When an alkali oxide modifies the pure boron oxide, the additional oxygen causes a conversion from the trigonal boron atoms BO 3 into 4-fold BO 4 coordinated boron atoms. Each BO 4 structural group is negatively charged and the four oxygens are included in the network as bridging oxygen. These units are responsible for the increase in the connectivity of the glass network. As a result, the degree of the structural compactness and modification of the geometrical configuration in the glass network can vary with a change in the composition [4,5] . In borotellurite glasses, the TeO 4 units and BO 4 units have a strong tendency to link with each other to form BTeO 3,5 units, which results in a higher connectivity in the glass network just like BPO 4 units in borophosphate glasses [6] . In this article the elastic moduli of borotellurite glasses will be discussed. Information about the structure of the glass can be deduced by calculating the number of network bonds per unit volume, the average stretching force constant, the average ring size and the average cross- link density. The theoretical values of ultrasonic activation energy and elastic moduli are calculated and compared with the corresponding experimental values. MATERIALS AND METHODS For the present studies, a binary TeO 2 -B 2 O 3 glass system was prepared with different mol percent TeO 2 . The binary TeO 2 -B 2 O 3 glasses were synthesized by the method mentioned elsewhere [7] . The prepared samples were cut into required dimension for ultrasonic velocity measurement. For ultrasonic velocity measurement of the glass sample, MATEC MBS 8000 was used. All measurements were taken at 5 MHz frequency and at room temperature. The density of the glasses was determined by Archimedes method with acetone as buoyant liquid. Theory: For a three dimensional one component oxide glass of A-O bond (A= cation, O= oxygen), the bulk modulus (K bc ) according to the bond compression model [8] is given by equation 2 b bc nf K = r 9 (1) where r is the bond length between cation and anion, f is the average stretching force constant and n b is the number of network bond per unit volume of the glass is given by