Correlation between Luminescence Quantum Efficiency and Structural Properties of Vanadate Phosphors with Chained, Dimerized, and Isolated VO₄ Tetrahedra

Abstract

The internal luminescence quantum efficiency and color properties of AVO3 (A: Li, Na, K, Rb, and Cs), M2V2O7 (M: Mg, Ca, Sr, Ba, and Zn), and M3V2O8 (M: Mg, Ca, Sr, Ba, and Zn) have been investigated. These vanadate phosphors exhibited broadband emission from 400 nm to over 800 nm due to the one-electron charge transfer transition in the VO4 tetrahedra, and the color of the luminescent materials ranged from green to yellow-orange via white, corresponding to 0.277 < x < 0.494 and 0.389 < y < 0.488 on the CIE chromaticity diagram. We found that the luminescence quantum efficiency of the vanadate phosphors with VO4 tetrahedra was strongly enhanced by the strong interaction between V ions and the weak interaction between V and A(M) ions in the crystal structures. We hypothesize that the long exciton diffusion lifetime induced by these structural features enhanced luminescence, leading to high quantum efficiency.

Luminescence of the self-activated vanadate phosphors Na2LnMg2V3O12 (Ln=Y, Gd)

“…As depicted in Fig. 3c, the molecular orbitals of the V 5 þ ion are expressed as a ground state 1 A 1 and four excited states 1 T 1 , 1 T 2 , 3 T 1 , and 3 T 2 [23]. The excitation bands for Ex 1 and Ex 2 in the PLE spectra are assigned to the partly enabled spin-allowed transitions from the ground state to the excited state 1 A 1 -1 T 1 and 1 A 1 -1 T 2 , respectively.…”

“…The emissions are attributed to the T 2 -1 A 1 (Em 1 ) and 3 T 1 -1 A 1 (Em 2 ) forbidden transitions in the ideal T d symmetry. Nonetheless, the spin-forbidden transitions partially allowed on account of the spin-orbit interaction, which relays on the spin and orbital angular momentums as well as the central-field potential [24], so the distortion degree of VO 4 tetrahedron from the ideal T d symmetry improves the spin-orbit interaction and enhances the intensity of [VO 4 ] 3À emission [23,25]. So, as mentioned earlier, the phosphor Na 2 GdMg 2 V 3 O 12 has more intense emission than Na 2 YMg 2 V 3 O 12 because of stronger distortion.…”

Vanadate Phosphors for Energy Efficient Lighting

“…The added PEG forms a polymeric network and prevents non-uniform aggregation. Park and Nam [19] synthesized high-quality (Y 0.5 Gd 0.5 ) 0.94-x Al x Eu 0.06 VO 4 (x=0 to 0.04) red phosphors by ultrasonic spray pyrolysis technique and Chang et al [20] [21][22][23][24][25]. It is well known that vanadate compounds enjoy a special place as they are capable of luminescing both with and without activators.…”

Fabrication of Zn₃V₂O₈ yellow phosphor from precursor aqueous solution of zinc acetate and peroxo-isopolyvanadic acid

“…Zn 3 V 2 O 8 is a candidate, for the following reasons. The Zn 3 V 2 O 8 lattice is assembled from layers of Zn octahedra connected by vanadate groups, 2) and the broadband emission spectra of Zn 3 …”