Concentration dependence of the Bi3+ luminescence in LnPO4 (Ln = Y3+, Lu3+)

Abstract The spectroscopic properties of the Bi 3+ ion (6s 2 ) as a function of its concentration is examined to clarify the nature of optical transitions that are responsible for the low- and high-energy bands in the emission spectra of LnPO 4 :Bi 3+ (Ln 3+  = Y 3+ , Lu 3+ ). Our investigations conclude that (1) the high-energy emission band is due to isolated Bi 3+ ions ( 3 P 0,1  →  1 S 0 transition), and (2) pairs or cluster of Bi 3+ ions is responsible for the low-energy emission band. We discuss our results in view of a recent interpretation, which tentatively assigns the low-energy emission band to a metal-to-metal (Bi 3+ –Y 3+ ) charge transfer transition. The Stokes shift of Bi 3+ luminescence in a site with dodecahedral coordination is examined in this work.