Judd–Ofelt analysis, structural and spectroscopic properties of sol–gel derived LaNbO4:Dy3+ phosphors

Abstract

La1−xNbO4:xDy3+ phosphors were synthesized through sol–gel route. XRD analysis confirms pure fergusonite monoclinic structure of La1−xNbO4:xDy3+ phosphor. The FTIR and Raman spectra show the vibrational modes present in La1−xNbO4:xDy3+ phosphor. The surface morphology and internal microstructure of the prepared phosphor were analysed by scanning electron microscopy and transmission electron microscopy and its microstructure is useful for better luminescence efficiency. UV–VIS-NIR spectrum of La1−xNbO4:xDy3+ phosphor was analysed on the basis of Judd–Ofelt theory and the J–O intensity parameters (Ωλ) were calculated. The radiative properties such as radiative transition probability, branching ratio, stimulated emission cross-section and optical gain were investigated using J–O intensity parameters. Energy transfer process between host and Dy3+ ions was studied at host excitation of 251 nm and tunable color emission from blue to near white was obtained with increasing concentration of Dy3+ ion. Excitation into 4f levels of Dy3+ ions at 351 nm show cool white light emission and the corresponding decay time, color coordinates and color correlation temperature were calculated. The results indicate that the prepared phosphor produce white light emission from a single phase host and can be used for near ultraviolet pumped white light emitting diode (NUV WLED) applications.