title: Luminescence Mechanistic Study of BaLaGa3O7:Nd Using Density Functional Theory Calculations.
abstract: BaLaGa3O7:Nd (BLGO:Nd) has been investigated as a laser crystal material for about three decades. In the present work, the luminescence mechanism of BLGO:Nd is clarified by density functional theory (DFT) calculations. Structural optimization was first performed on the constructed supercell to obtain the equilibrium geometry. On the basis of the optimized crystal, the electronic structures of the BLGO host (without and with single defects) and the BLGO:Nd phosphor (without and with neighboring defects) were comprehensively investigated. Three important features are revealed by theoretical analyses. First, single defects in BLGO have little effect on the light emission, although the impurity levels appeared within the band gap. Second, luminescence can be realized by the introduction of Nd ions. Calculations of optical properties demonstrated that parity-forbidden transitions among the 4f levels are partially allowed because the mixing of 4f and 5d configurations occurs at higher empty 4f levels. It is thus clear that the electronic transitions between occupied 4f and empty 4f-5d states are electric-dipole-allowed. Therefore, light emission in BLGO:Nd can be achieved in the electronic transition process of Nd 4f electrons → empty 4f-5d levels → empty 5d levels → Nd 4f levels. The neighboring intrinsic defects play only an auxiliary role in prolonging the decay time. Third, co-doping of Tb in BLGO:Nd is considered to be beneficial to luminescence in theory because of its shallow to deep distribution of impurity orbitals in the band gap. Therefore, BLGO:Nd co-doped with other lanthanide ions will offer guidelines in the search for the best luminescent materials.
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.|University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors.forename: Junling
authors.initials: J
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Congting
authors.initials: C
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.|University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors.forename: Chuangang
authors.initials: C
authors.lastname: Yao
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.|University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors.forename: Lifang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Fen
authors.initials: F
authors.lastname: Yao
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Dongfeng
authors.initials: D
authors.lastname: Xue
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Jian
authors.initials: J
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Zhang