ABSTRACT
Luminescence of Bi3+-related centers was studied in various materials (alkali halides, alkaline-earth oxides, sulphates, and phosphates, rare earth oxide-based materials, etc.) starting from 1960s (see, e.g., [62-82] and references therein). The Bi3+-doped rare earth aluminate and gallate garnets and rare earth silicates, where a Bi3+ ion substitutes a trivalent rare earth ion, were considered as perspective materials for scintillators due to an intense and fast Bi3+-related luminescence [78, 80, 81]. Besides, it was found that in SCF of Y3Al5O12:Bi and Lu3Al5O12:Bi, grown by the LPE method from the melt-solution based on a Bi2O3 oxide flux, a large and variable concentration of Bi3+ ions can be achieved [80, 81]. The interest in Bi3+-doped compounds has recently re-appeared in connection with the preparation of phosphors for new generation of solid state light sources, so-called white LED [83-85]. Bi3+ ions are used to efficiently absorb light in near UV and transfer the energy to other emission centers in the green-red spectral range. Therefore, it is of interest to study the luminescence characteristics of various Bi3+-doped materials in order to obtain information on the nature of
luminescence centers, origin and structure of their relaxed excited states (RES), and on the processes taking place in the excited states.This chapter reviews the detailed and systematic study of luminescence characteristics of Pb-and Bi-related centers in aluminum perovskites and garnets [86-92] and oxyorthosilicates [93-96] carried out by the time-resolved spectroscopy methods in the 4.2-400 K temperature range. The characteristics of the SCF with different Pb or Bi contents were compared with those of the corresponding SC and the substrates used at the SCF preparation. As a result of these studies, the spectral bands, arising from Pb-and Bi-related centers of different types, were identified and their RES structure and parameters defined. The processes of energy transfer from the host lattice to the impurity (Ce3+, Pr3+) ions and between various Pb-related centers and the impurity ions were studied, and the influence of various Pb-related centers on the luminescence characteristics of the impurity ions was clarified.
