Luminescence and excited state dynamics in Bi3+-doped LiLaP4O12 phosphates

• Published in: Journal of luminescence 2016-08, Vol.176, p.324-330
• Main Authors: Babin, V., Chernenko, K., Demchenko, P., Mihokova, E., Nikl, M., Pashuk, I., Shalapska, T., Voloshinovskii, A., Zazubovich, S.
• Format: Article
• Language: English
• Subjects: Bi powders; Bi3+ centers; Excited states; LiLaP4O12; Photoluminescence; Time-resolved spectroscopy
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2016.04.012

Photo- and X-ray-excited luminescence characteristics of Bi-doped LiLaP4O12 phosphates with different bismuth contents (from 1 to 25 at% in the melt) are investigated in the 4.2–300K temperature range and compared with the characteristics of the undoped LiLaP4O12 phosphate. The broad 2.95eV emission band of LiLaP4O12:Bi excited around 5.4eV is found to arise from the bismuth dopant. Relatively large FWHM and Stokes shift of the emission band and especially the data on the low-temperature decay kinetics of the 2.95eV emission and its temperature dependence, indicating a very small spin-orbit splitting energy of the corresponding excited state, allow the conclusion that this emission arises from the radiative decay of the triplet state of an exciton localized around a Bi3+ ion. No spectral bands are observed, arising from the electron transitions between the energy levels of Bi3+ ions. Phenomenological model is proposed for the description of the excited state dynamics of the Bi3+-related localized exciton in LiLaP4O12:Bi and the parameters of the triplet localized exciton state are determined. Keywords: Photoluminescence; Time-resolved spectroscopy; Excited states; Bi3+ centers; LiLaP4O12:Bi powders