Physicochemical properties of Li3Ba2La3(MoO4)8:Eu,Tb red-emitting phosphor for solid state white lamps

In this work, combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light lamps. We synthesized a material with emission wavelength at lem = 617 nm, excited under long UV-blue wavelength based on Eu3+, Tb3+-activated molybdates Li3Ba2(La1-x-yEuxTby)3(MoO4)8 with 0 < x < 1 and 0 < y < 1. A series of powder samples were produced by the combustion method and post-annealed at 800 & DEG;C in air. The crystalline phase formation was investigated by X-ray diffraction, which reveals the monoclinic C2/c (15) space group. It is observed that crystalline structure and morphology are preserved when the host lattice is doped with Eu3+ or Tb3+ single ions and co-doped with both ions at different doping concentrations. A detailed characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) shows a similar morphology in all samples: rather large (1-7 mm) agglomerate particles with irregular shapes and surrounded by smaller nanoparticles of 50 nm in size. UV-visible absorption spectra confirm the presence of Eu3+ and Tb3+ ions. The luminescent properties of the obtained phosphors were studied in detail. Cathodoluminescence measurements indicate that the best emission intensity is for Eu3+:Tb3+ doping ratios of 80:0, 90:0 and 20:80. On the other hand, samples with 80:0, 60:40, and 20:80 doping ratios show the highest intensity in a detailed photoluminescence analysis and they exhibit the highest quantum yield values. A complete and efficient energy transfer from the sensitizer Tb3+ to the activator Eu3+ is observed in all co-doped phosphors post-annealed at 800 & DEG;C for 4 h. Thus, the Li3Ba2La3(MoO4)8:Eu3+,Tb3+ materials fabricated by combustion synthesis are excellent phosphors for being applied as red-emitting component in solid-state white-light lamps due to an improved color rendering index (CRI) that can be obtained under long UV-blue excitation wavelengths.& COPY; 2022 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Automated summary

A red-emitting phosphor material was successfully synthesized using combustion synthesis method, and its properties were extensively studied. The material showed great potential for applications in solid-state white-light lamps due to its improved color rendering index.