Optical Transitions near the Fundamental Absorption Edge and Electronic Structures of YAl₃(BO₃)₄:Gd³⁺

Abstract

Optical properties of Gd3+ ions doped in YAl3(BO3)4 are investigated as a new UV phosphor under excitation of VUV radiation. A strong emission line at 3.96 eV (313 nm) corresponding to the transitions from the 6P7/2 to 8S7/2 states of Gd3+ ions is observed. We performed the Rietveld refinement using an X-ray diffraction result to obtain the structural parameters of a synthesized YAl3(BO3)4:Gd3+ phosphor. From the result, it is shown that the refined crystal structure of YAl3(BO3)4:Gd3+ phosphors is slightly distorted. The electronic structures have been calculated using the relativistic discrete variational Xα method. The calculations indicate that the optical properties of a non-doped YAl3(BO3)4 crystal near the fundamental absorption edge are characterized by the electronic transitions from O 2 p valence states to B 2 p conduction states. On the other hand, it is found that the origin of the absorption edge of YAl3(BO3)4:Gd3+ phosphor is due to the transitions from O 2 p states to mixed states of mainly B 2 p and Y 4d orbitals.

Luminescence properties of YAl3(BO3)4:Gd3+ phosphors substituted with Sc3+ ions

“…The band gap energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is estimated to be 5.65 eV. We reported that the lower edge of the conduction band of [YAl 6 B 8 O 42 ] 39À cluster is composed of mainly B 2p orbital and Y 4d orbital [3], and the band gap energy was evaluated to be 7.32 eV. From theses results, we concluded that the fundamental absorption edge of fictitious ScAl 3 (BO 3 ) 4 originates from the significant contribution of O 2p -Sc 3d transitions and is located at lower-energy side than that of YAl 3 (BO 3 ) 4 single crystal.…”

“…Recently, we reported the electronic structures of nondoped YAl 3 (BO 3 ) 4 crystal and YAl 3 (BO 3 ) 4 :Gd 3+ phosphor [3]. The results suggested that the bottom of conduction band was composed of mainly B 2p orbital and Y 4d orbital, and YAl 3 (BO 3 ) 4 :Gd 3+ phosphor had a lower conduction band edge due to a slight distortion of the BO 3 triangle in YAl 3 (BO 3 ) 4 crystal structure.…”

Crystal and electronic structures, luminescence properties of Eu2+-doped Si6−zAlzOzN8−z and MySi6−zAlz−yOz+yN8−z−y (M=2Li, Mg, Ca, Sr, Ba)

“…Using the relativistic DV-Xa code [24][25][26][27] presumably placed in the most promising site in b-S 3 N 4 at 2b (0,0,0), where the six-ring (Si/Al)N 4 tetrahedra constructs a big channel within a 2 Â 2 Â 2 supercell (Fig. 1a).…”

Photoluminescence properties and local electronic structures of rare earth-activated Sr3AlO4F

“…The local electronic structures, viz., the energy levels of the atomic orbitals and the density of states (DOS) of Ce 3+ -doped Sr3AlO4F, were calculated by using the relativistic DV-X␣ method based on first-principles molecular orbitals (MO) approach [23][24][25][26]. On the basis of the crystal structure of Sr3AlO4F [20,21], the cluster models of [Ce(I)O8F2] −15 and [Ce(II)O6F2] −11 were built up for Ce 3+ -doped Sr3AlO4F corresponding to the point groups of D4 and Cs symmetry, respectively, in which the Ce 3+ ions are assumed to be randomly substituted for the two Sr ions.…”