Optical band gap studies on xPb3O4–(1−x)P2O5 lead[(II, IV)] phosphate glasses

A series of glasses in the xPb₃O₄–(1−x)P₂O₅ (red lead phosphate) (RLP) system with ‘x' varying from 0.075 to 0.4 were prepared by the single-step melt quenching process from Pb₃O₄ and NH₄H₂PO₄. The optical absorption spectra of these glasses have been recorded in the ultraviolet region from 200 to 400 nm and the fundamental absorption edges have been identified. The optical band gap E_opt values have been determined for all the glasses using the known theories. The (E_opt) values vary from 4.90 to 3.21 eV the highest being 4.57 eV, corresponding to the most stable glass of x=0.225. The absorption edge is attributed to the indirect transitions and the origin of the Urbach energy ΔE is suggested to be thermal vibrations. These glasses promise as potential candidates for application in optical technology compared to simple xPbO–(1−x)P₂O₅ (lead phosphate) (LP) glasses.