title: Coexistence phenomenon of Ce3+-Ce4+and Eu2+-Eu3+in Ce/Eu co-doped LiBaB9O15phosphor: luminescence and energy transfer.
abstract: Ce/Eu-doped LiBaB9O15(LBB) samples were prepared via conventional high temperature solid state reactions. The XRD patterns, crystal structures, luminescence properties, and decay times were investigated systematically. Ce3+ions exist in LBB:xCe3+that were synthesized in a reducing atmosphere and in an air atmosphere. However, we observed Eu2+ions in LBB:yEu2+in a reducing atmosphere and Eu3+ions in LBB:zEu3+in an air atmosphere. LBB:0.05Ce3+,yEu2+phosphors synthesized in a reducing atmosphere only possess Ce3+and Eu2+and exhibit a broad excitation band ranging from 350 to 425 nm. A reduction phenomenon of Eu3+→ Eu2+and coexistence of Ce4+, Ce3+, Eu2+and Eu3+were observed when LBB:0.05Ce,wEu phosphors were synthesized in an air atmosphere. There are three processes in LBB:0.05Ce,wEu, i.e., energy transfers from Ce3+to Eu2+and from Eu2+to Eu3+, and metal-metal charge transfer (MMCT) between Ce3+and Eu3+. Moreover, the MMCT process is dominant in LBB:0.05Ce,wEu due to less efficient energy transfer from Ce3+to Eu2+. Moreover, the CIE coordinates of LBB:0.05Ce,wEu vary systematically from light blue (0.313, 0.129) to red (0.589, 0.315) for LBB:0.05Ce3+,wEu synthesized in air with the changes in Eu ion concentration. Thus, we can control the color by controlling the synthesis atmospheres.
authors.affiliation: College of Physics Science & Technology, Hebei Key Lab of Optic-Electronic Information and Materials, Hebei University, Baoding 071002, China. li_panlai@126.com wangzj1998@126.com.
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.affiliation: College of Physics Science & Technology, Hebei Key Lab of Optic-Electronic Information and Materials, Hebei University, Baoding 071002, China. li_panlai@126.com wangzj1998@126.com.
authors.forename: Panlai
authors.identifier: http://orcid.org/0000-0003-0972-9343
authors.initials: P
authors.lastname: Li
authors.affiliation: College of Physics Science & Technology, Hebei Key Lab of Optic-Electronic Information and Materials, Hebei University, Baoding 071002, China. li_panlai@126.com wangzj1998@126.com.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Wang
authors.affiliation: College of Physics Science & Technology, Hebei Key Lab of Optic-Electronic Information and Materials, Hebei University, Baoding 071002, China. li_panlai@126.com wangzj1998@126.com.
authors.forename: Shuchao
authors.initials: S
authors.lastname: Xu
authors.affiliation: College of Physics Science & Technology, Hebei Key Lab of Optic-Electronic Information and Materials, Hebei University, Baoding 071002, China. li_panlai@126.com wangzj1998@126.com.
authors.forename: Qiongyu
authors.initials: Q
authors.lastname: Bai
authors.affiliation: College of Physics Science & Technology, Hebei Key Lab of Optic-Electronic Information and Materials, Hebei University, Baoding 071002, China. li_panlai@126.com wangzj1998@126.com.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Yang