Color - Tunable Phosphors in Weberite Type System, La₃ SbO₇ :Bi³⁺ , Eu³⁺ for Near-UV LED Applications

Abstract

A new series of color tunable from yellow to near white emitting phosphors, La3SbO7:xBi3+, yEu3+ were prepared using a conventional solid state method and its structural, morphological, absorbance and photoluminescence properties and lifetime measurements were carried out to analyze the phosphor characteristics. The La3SbO7:Bi3+ phosphors crystallize into a phase pure weberite type structure with good particle morphology. Upon UV light excitation at 315 nm, these phosphors show broad band emission in the blue green region centered near 517 nm owing to the 3P1‐1S0 transitions of the Bi3+ activator. Critical emission quenching of La3SbO7:xBi3+ samples was observed at x = 0.04. Eu3+ is co‐doped with La3SbO7:0.04Bi3+ blue green phosphor to incorporate the red component to make a full color emission phosphor. The effective energy transfer from Bi3+ to Eu3+ ions has been assessed using Dexter's theory indicating resonance type through dipole‐quadrupole interaction. Further the decreasing trends in lifetime measurements confirm the existence of energy transfer process from Bi3+ to Eu3+. The near white light emitting phosphor La3SbO7:xBi3+, yEu3+ can be realized by adjusting the concentrations of the Bi3+ and Eu3+ with chromaticity coordinates: (0.30,0.48). The above results suggest that the developed phosphor could be potential to be used as a single phase white emission phosphor for n‐UV LED applications.

High-Efficiency Continuous-Luminescence-Controllable Performance and Antithermal Quenching in Bi3+-Activated Phosphors

“…Moreover, the unequal valence states further prove that Bi 3+ ions will not occupy the [SbO 6 ] site. However, the ionic radii of La1 3+ ( r = 1.16 Å) and Bi 3+ ( r = 1.17 Å) are extremely close in dodecahedral structure, which means that Bi 3+ is supposed to replace the [La1O 8 ] site Figure b represents the crystal structure schematic diagram of two chemical substitution strategies (Gd replaces La and Nb replaces Sb).…”

Energetics of Formation and Disordering in Rare Earth Weberite RE3TaO7 Materials

“…RE 3 MO 7 (RE 3+ = rare earth; M 5+ = Nb, Ru, Sb , Ta, Re, Os) materials are a family of rare earth rich oxides which adopt one such weberite-derived 2O–III polytype structure with a cation ratio of 3:1. ,− RE 3 MO 7 oxides are called as a weberite-type or La 3 NbO 7 -type structure as they are structurally derived from weberites. These oxides have been investigated for various technological applications, − but their thermodynamic properties and energetics of order–disorder have not been studied extensively. RE 3 NbO 7 is the only series of compounds in the weberite family for which thermodynamic properties have been studied by high temperature oxide melt solution calorimetry .…”