LUMINESCENCE OF BI3+ IONS AND ENERGY-TRANSFER FROM BI3+ IONS TO EU3+ IONS IN SILICA GLASSES PREPARED BY THE SOL-GEL PROCESS

Luminescence of Bi3+ ions and energy transfer from Bi3+ ions to Eu3+ ions in silica glasses prepared by the sol-gel process have been investigated. The results showed that the excitation band of Bi3+ ions corresponds to the S-1(0) --> P-1(1) transition and emission spectra consists of a single broad band without structure centred at 395 nm, which corresponds to P-3(1) --> S-1(0) transition. When a small amount of Bi3+ ions was introduced to 1 mol% Eu3+ ions the doped silica gel glass emission intensity of Eu3+ ions got significantly stronger, which suggests very efficient energy transfer from Bi3+ ions to Eu3+ ions. It can be assigned to significant energy overlap between the emission band of the Bi3+ ion and the excitation band of the Eu3+ ion. However, due to a larger energy overlap between emission and excitation bands of Bi3+, when Bi3+ ion concentration in silica gel glasses was more than 0.5 mol% the probability of energy transfer between Bi3+ ions increased rapidly and the probability of energy transfer from Bi3+ ions to Eu3+ ions decreased relatively. As a consequence, the sensitized effectiveness of the Bi3+ ion on the emission spectrum of the Eu3+ ion drastically decreased with increasing Bi3+ ion concentration.