Structural and optical characterizations of cool white light emitting Ba2Zn2La4O10 :Dy3+ nanophosphor for advanced optoelectronic applications

Dy3+-doped Ba2Zn2La4O10 (1-6 mol%) white light emitters were successfully developed via simple and economic Solution Combustion (SC) route. The 3D crystal structural, morphological and spectrofluorophotometric studies were systematically carried out using XRD (X-ray diffraction), SEM & TEM (scanning and transmission electron microscopy) and PL (photoluminescence) measurements. Rietveld structural refinement confirmed the pure tetragonal phase [space group-I4/mcm (140)] of Ba2Zn2La3.88Dy0.12O10 composition. Highly aggregated particles with irregular morphology in nano-range (15-45 nm) was observed in SEM & TEM observations and the elemental analysis using electron diffraction studies (EDS) confirmed the presence of all existing elements in optimum composition (3 mol%). An excitation of 353 nm wavelength provided blue (488 nm) & yellow (577 nm) emissions caused by F-4(9/2) -> H-6(15/2, 13/2) transitions in Dy3+ ions. Critical separation among neighboured Dy3+-Dy3+ ions for energy transfer process was determined to be 16.39 angstrom, which helped to select the actual interaction type (d-d) behind concentration quenching phenomena. The detailed luminescence decay curve analysis provided the radiative lifetime (0.55 ms), quantum efficiency (88%) and non-radiative relaxation rate (259.52 s(-1)) for lowest emitting state (F-4(9/2)) in optimized phosphor composition. The calculated CIE coordinates (x = 0.2809, y = 0.2715) and CCT (similar to 11,000 K) affirmed the cool white light emission from Ba2Zn2La3.88Dy0.12O10 nanophosphor composition. All the studies demonstrated the significant role of NUV-excited Ba2Zn2La4O10:Dy3+ nanophosphor in cool white LEDs and optoelectronic devices.