Compositional Dependence of Elastic Modulus in Binary Tellurite Glasses

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Elastic moduli of some binary tellurite glasses were measured by using a cube-resonance method. The glass systems employed were MgO-TeO₂, ZnO-TeO₂, MoO₃-TeO₂, and WO₃-TeO₂. Young's moduli of most glasses can be predicted using the compositional parameters based on the Makishima-Mackenzie theory. In the systems containing divalent cations (Mg²⁺ or Zn²⁺), Young's modulus of MgO-TeO₂ glass was larger than that of ZnO-TeO₂ glass because of the higher dissociation energy of MgO. In the case of the glasses containing hexavalent cations (Mo⁶⁺ or W⁶⁺), although the dissociation energy and the packing factor of MoO₃ and WO₃ are comparable with each other, Young's modulus of MoO₃-TeO₂ glass was smaller than that of WO₃-TeO₂ glass. This is due to the change in oxygen coordination state of a hexavalent cation. A less contribution of doubly bonds around Mo⁶⁺ to the mean bond-strength in glass would be one of the reasons for the difference in Young's modulus. The larger molar volume of MoO₃-TeO₂ glass also supports this loose structure.