STUDIES ON THE ROLE R2ON (R = GA AND CR, N = 3, R = NB AND TA, N = 5)IN I(2)O-CENTER-DOT-0.5(XR(2)O(N)CENTER-DOT(1-X)B2O3) GLASS SYSTEM

The influence of the addition of R2On (R = Ga and Cr, n = 3; R = Nb an d Ta, n = 5) on the thermal, electrical and structural properties of 0 .5Li(2)O . 0.5{xR(2)O(n).(1 - x)B2O3} glassy systems has been investig ated. Results of X-ray photoelectron spectroscopy (XPS) and Fourier tr ansform infrared (FT-IR) have shown that Ga2O3 is in 4-coordination, N b2O5, Ta2O5 and Cr2O3 are in 6-coordination in the above ternary glass es. Ga2O3, Nb2O5 and Ta2O5 act as both a network former and modifier a t different ranges of composition. With the incorporation of Ga2O3, Nb 2O5 and Ta2O5 into lithium berate binary glasses, the de conductivity of the ternary systems shows two maxima which are due to the increase in the radius of the network doorway and the network modification effe ct, respectively. For 0.5Li(2)O . 0.5{xGa(2)O(3).(1 - x)B2O3} system, the glass transition temperature (T-g) decreases with the increase in Ga2O3 content. For 0.5Li(2)O . 0.5{xNb(2)O(5).(l - x)B2O3} system, T-g reaches a minimum at the composition corresponding to Z= Nb2O5 conten t = 0.5 x 100 mol% = 0.2 mol%. When Z greater than or equal to 0.4 mol %, Tn increases with the increase in Nb2O5 content. Furthermore, the a ddition of Cr2O3 and Ta2O5 into lithium berate glass causes an increas e in T-g. (C) 1998 Elsevier Science S.A. All rights reserved.