JUDD-OFELT ANALYSIS OF Tb3+ AND UPCONVERSION STUDY IN Yb3+-Tb3+ CO-DOPED CALIBO GLASSES
Abstract: We report on the study of the spectroscopic properties in Ytterbium–Terbium (Yb3+-Tb3+) co-doped calcium lithium borate (CaLiBO) glasses, with the study’s focus being on the upconversion process. Intensity parameters Ωλ for CaLiBO:Tb3+ are determined by the Judd–Ofelt method to be Ω2 = 15.5 × 10-20 cm2, Ω4 = 1.90 × 10-20 cm2 and Ω6 = 3.69 × 10-20 cm2. We have also obtained electric-dipole (and magnetic-dipole) radiative transition probabilities, branching ratios, and lifetime for the Tb3+: 5 D4 and 5 D3 levels. In addition, an evaluation of the upconversion processes by luminescence and time-resolved spectroscopy were carried out. The upconversion rise and decay times, energy transfer probability from Yb3+ to Tb3+ ions, and the efficiency of the processes that depopulate the Tb3+: 5 D4 level after resonantly pumping the Yb3+: 2 F5/2 level were estimated. Our results showed that a cooperative energy transfer (CET) from two Yb3+ ions to one Tb3+ ion is the origin of the Tb3+ upconversion luminescence in the visible region. While, CET followed of the cross relaxation or/and excited state absorption is responsible for the upconversion luminescence in the ultraviolet region.
Author(s): Terra, IAA; Borrero-González, LJ; Almeida, JMP; Hernandes, AC; Nunes, LAO
Quim. Nova
Published: 22/01/2020
DOI: http://dx.doi.org/10.21577/0100-4042.20170465
