STRUCTURAL INVESTIGATION OF Fe2O3-Bi2O3-B2O3 GLASSES

The structure of xFe(2)O(3)center dot(30-x)Bi2O3 center dot 70B(2)O(3) and xFe(2)O(3)center dot(50-x)Bi2O3 center dot 50B(2)O(3) glasses (mol%) was investigated by FTIR, XRD and SEM. Increasing Fe2O3 content causes decreasing in the fraction N-4 of four coordinated boron atoms of both series. FTIR analyses indicate that Fe2O3 tends preferentially to form its former matrix and the majority of BO4 units are modified by Bi3+ ions. XRD patterns confirm that only alpha-Fe2O3 crystalline phase appears in the glasses with Fe2O3 >= 15 mol% for the first group and Fe2O3 >= 25 mol% for the second one. 50Bi(2)O(3)-50B(2)O(3) glass in the second group has tendency to crystallization when heat treated. SEM shows that spherical particles are separated from the main matrix with different sizes in both glass groups. There is a linear decrease of density in both series with replacing Bi2O3 by Fe2O3. The molar volume seems to be constant in the first group, whereas it decreases in the second one. Calculated density and molar volume are in a good agreement with the experimental data.