Luminescence and X-ray absorption studies on 0.5% Ce³⁺ doped BaCa₂MgSi₂O₈ phosphor

Abstract

0.5% Ce(3+) doped BaCa2MgSi2O8 phosphor was prepared by a conventional solid state reaction method. Luminescence spectra as well as fluorescence decay were monitored in the VUV-UV range. Ce(3+) emissions are assigned to cerium ions on a Ba(2+) site, and the five 4f-5d excitation bands of Ce(3+) were determined at low temperature. The light yield is estimated to be around 10,600 ph MeV(-1) under X-ray excitation. X-ray absorption near-edge structure (XANES) was explored to study the energy transfer efficiency to optical centers from each element in the phosphor; the results show that the contributions to luminescence are not identical for each element.

VUV–UV–vis Luminescence, Energy Transfer Dynamics, and Potential Applications of Ce3+- and Eu2+-Doped CaMgSi2O6

“…Consequently, the exciton creation energy ( E ex ) of CaMgSi 2 O 6 can be estimated to be ∼7.85 eV. This value is comparable to that of alkaline earth silicates BaMg 2 Si 2 O 7 (∼7.65 eV) and BaCa 2 MgSi 2 O 8 (∼7.42 eV) but slightly higher than those of Ba 3 MgSi 2 O 8 (∼7.12 eV) and Ba 2 MgSi 2 O 7 (∼6.89 eV) in energy. − Accordingly, the band gap energy of CaMgSi 2 O 6 can be evaluated by the sum of host exciton creation energy ( E ex ) and the exciton binding energy . Two empirical approaches have been proposed to estimate the exciton binding energy.…”

“…The 5d centroid energy has been considered to related to the nephelauxetic effect, the covalency between anions and Ce 3+ , and the spectroscopic polarizability of anion ligands. Consequently, the nephelauxetic effect, covalence, or spectroscopic polarizability of the following alkaline earth silicates increases with the relative order of BaCa 2 MgSi 2 O 8 (4.90 eV) < Ba 3 MgSi 2 O 8 (4.95 eV) < Ba 2 MgSi 2 O 7 (4.97 eV) < CaMgSi 2 O 6 (∼5.07 eV) < BaMg 2 Si 2 O 7 (5.12 eV). − The emission [curve (b), λ ex = 291 nm] spectrum of the Ca 0.998 Ce 0.001 Na 0.001 MgSi 2 O 6 sample at 10 K in Figure shows typical doublet emission bands at ∼378 nm (2.65 × 10 4 cm –1 , 3.28 eV) and ∼351 nm (2.85 × 10 4 cm –1 , 3.53 eV) of Ce 3+ , which arise from the transitions from the relaxed lowest 5d state of Ce 3+ to 4f ground states 2 F 7/2 and 2 F 5/2 , respectively . Their energy difference is about 2.00 × 10 3 cm –1 , corresponding to the spin–orbit splitting of the 2 F J ground-state term of Ce 3+ .…”