Glasses with compositions xFe_2O_3.(40-x)M.60B_2O_3 (M= Bi_2O_3 and PbO) have been prepared using the standard melt-quenching technique. Each sample was characterized by study of XRD and SEM patterns. The structural properties such as glass transition temperature, density, molar volume etc. have been studied of each sample. The glass transition temperature increases which is due to the replacing of B-O-B bonds by more durable B-O-Fe~(2+) or B-O-Fe~(3+) bonds with increasing Fe_2O_3 content whereas the density decreases is due to the replacement of heavier cation (Bi or Pb) by the lighter one (Fe) in both the series. The density of Fe_2O_3-PbO-B_2O_3 (FPB) glass samples is lower than that of corresponding Fe_2O_3-Bi_2O_3-B_2O_3 (FBB) suggesting thereby the addition of PbO with Fe_2O_3 produces more non-bridging oxygens (NBOs) than Bi_2O_3.
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