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 λ em = 617 nm, excited under long UV-blue wavelength based on Eu 3+ , Tb 3+ -activated molybdates Li 3 Ba 2 (La 1– x – y Eu x Tb y ) 3 (MoO 4 ) 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 °C in air. The crystalline phase formation was investigated by X-ray diffraction, which reveals the monoclinic C 2/ c (15) space group. It is observed that crystalline structure and morphology are preserved when the host lattice is doped with Eu 3+ or Tb 3+ 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 μm) agglomerate particles with irregular shapes and surrounded by smaller nanoparticles of 50 nm in size. UV–Visible absorption spectra confirmed the presence of Eu 3+ and Tb 3+ ions. The luminescent properties of the obtained phosphors were studied in detail. Cathodoluminescence measurements indicated that the best emission intensity was for Eu 3+ :Tb 3+ 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 a highest intensity in a detailed photoluminescence analysis was observed and they exhibited the highest quantum yield values. A complete and efficient energy transfer from the sensitizer Tb 3+ to the activator Eu 3+ was observed in all co-doped phosphors post-annealed at 800 °C for 4 h. Thus, the Li 3 Ba 2 La 3 (MoO 4 ) 8 :Eu 3+ ,Tb 3+ materials fabricated by combustion synthesis are excellent phosphors for their application 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. Combustion synthesis used to fabricate red-emitting phosphors activated by a blue LED.