Raman studies and optical properties of some (PbO) x (Bi 2 O 3 ) 0.2 (B 2 O 3 ) 0.8− x glasses

Five (PbO) x (Bi 2 O 3 ) 0.2 (B 2 O 3 ) 0.8− x glasses, where x = 0, 0.2, 0.3, 0.4 and 0.6, were prepared. The dilatometric glass transition temperature ( T g ) was found in the region 470 ( x = 0)≥ T g ( °C) ≥ 347 ( x = 0.6), and the density (ρ) varied within 4.57 ( x = 0) ≤ ρ (g/cm 3 ) ≤ 8.31 ( x = 0.6). Raman spectra indicated the conversion of BO 3 to BO 4 entities for low x values but for x > 0.3, namely, for x → 0.6, back‐conversion occurred, most probably. From the measurements of the optical transmission on very thin bulk samples, the room temperature optical gap values ( E g ) were determined to be in the range 4.03 ( x = 0)≥ E g (eV) ≥ 3.08 ( x = 0.6). The temperature ( T ) dependence of the optical gap ( E g (T)) in the region 300 ≤ T (K) ≤ 600 was examined and approximated by a linear relationship of the form of E g ( T ) = E g (0)− γ T , where γ × 10 −4 (eV/K) varied from 5.1 to 6.8. The non‐linear refractive index ( n 2 ) was estimated from the optical gap values and it was found to correspond to the n 2 values calculated from the experimental third‐order non‐linear optical susceptibility taken from the literature. Copyright © 2008 John Wiley & Sons, Ltd.