Novel Eu3+ doped Li2ZnTi3O8 phosphor: Synthesis, structural and optical characterization for white light emitting diodes

Abstract

Embracing phosphor converted white light-emitting diodes (pc-WLEDs) represent a significant step towards efficient and sustainable energy sources, herein we report the synthesis, structural and optical properties of Eu3+ doped Li2ZnTi3O8 phosphor for the first time. A series of Li2(1-x)ZnTi3O8:xEu3+ phosphors (x = 0, 0.02, 0.05, 0.08, 0.1 and 0.3 mol) were prepared by the high temperature solid state reaction method. The structural and morphological characterisation of prepared samples were done using X -ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed the cubic structure and purity of the samples with the incorporation of Eu3+ ions. The presence of functional groups was detected from FTIR and compositional elements from EDX. FESEM and TEM images revealed similar agglomerated block like structures. The optical properties were analysed using diffuse reflectance spectrum (DRS) and photoluminescence (PL) spectra. Under 309 and 393 nm excitation, characteristic emission peaks of Eu3+ ions corresponding to 5D0→ 7FJ (J = 0,1,2,3 and 4) transitions were observed in which the intense emission was recorded at 612 nm. Under both the excitations, the optimum concentration of prepared phosphor was 8 mol% (x = 0.08 mol) and the mechanism for concentration quenching was found to be dipole - dipole interaction. The decay lifetime of prepared phosphors was in the milliseconds range and the internal quantum efficiency was measured to be 48.91 %. Li2(1-x)ZnTi3O8: 0.08Eu3+ phosphor has an activation energy of 0.163 eV and holds good thermal stability. Also, for the optimum sample, the Commission International de I'Eclairage (CIE) coordinates were detected at (0.6333, 0.3663) and (0.6344, 0.3651) for 309 and 393 nm excitation respectively, which lies in the orange - red region with super color purity and warm correlated color temperature (CCT) values. Therefore, obtained results suggest that the prepared Li2(1-x)ZnTi3O8:xEu3+ phosphors are suitable candidates for its use in pc-WLEDs.