INVESTIGATION ON CALORIMETRIC AND ELASTIC PROPERTIES OF 50TeO2-(50-x)V2O5-xK2O GLASSY SYSTEMS

In this work, the thermal behavior of ternary glassy compositions of 50TeO(2)-(50-x)V2O5-xK(2)O compositions with 0 <= x <= 20 (in mol%) prepared using the press-melt quenching method has been investigated. By utilizing Makishima and Makenzie's theory, some elastic features such as Young's modulus, bulk modulus, and shear modulus were calculated indicating a strong relation between elastic properties and structure of glass. In addition, the heating rate dependence of T-g was investigated using different theoretical models describing the glass transition. The activation energy values (Delta H*) for 50TVK0, 50TVK5 and 50TVK10 at different heating-rate regions were obtained, using Kissinger and Moynihan models. The results from both models showed two different values for the activation energy in each heating rate region suggesting strong heating rate dependency of activation energy process. Furthermore the observed similarity in Delta H* values for both models suggests that both equations are useful in determining Delta H*. The fragility parameter (m=Delta H*/R.T-g) was calculated for the samples. The results shows 50TVK10 have the lowest fragility, 17.58, indicating this composition can be considered as strong glass with good resistance against thermal shocks. Also a logical correlation was found between kinetic fragility parameter and elastic modulus confirming agreement between experimental and theoretical results. The obtained data was studied in order to indicate of the influence of addition of K2O as network modifier on thermal stability, glass-forming tendency and fragility.