The optical properties of thallium,lead and bismuth in oxide glasses

Absorption, fluorescence, excitation and decay time measurements have been made on a range of glasses containing thallium, lead and bismuth. In calcium phosphate and sodium silicate glasses the bands in both absorption and emission have been assigned to the A band of the Seitz model. For the bismuth doped glasses the A band was always observed in absorption but the emission was very dependent upon glass composition. Configurational coordinate curves have been constructed for Tl⁺ and Pb² in a glass of composition CaO. P₂O₅. Coordinate diagrams are also used to explain the presence or absence of bismuth fluorescence in certain glass compositions. In some borate glasses containing bismuth a brown colouration was observed. This was probably due to particle separation. No A band emission was observed from bismuth in a calcium phosphate glass. Instead there was a faint red emission similar to the cathodoluminescent bands of crystalline calcium phosphates.