A study of phase evolution, crystallographic and down-conversion luminescent behaviour of monoclinic Y4Al2O9:Dy3+nanophosphors for white light applications

Undoped Y4Al2O9 and Dy3+ doped Y4Al2O9 nanophosphors have been synthesized through urea aided com-bustion approach. The monoclinic phase of undoped and Dy3+ doped Y4Al2O9 nanosamples are affirmed by the results of X-ray diffraction. Diffuse reflectance (DR) spectrum and an energy band gap (5.51 eV) value for optimized Y3.96Al2O9:0.04Dy3+ sample, calculated utilizing the Kubelka-Munk theory, demonstrated the good optical quality of nanosample. Transmission electron microscope confirms the nanosize particles with some agglomeration. The synthesized nanosamples are well excited at 348 nm, exhibited yellowish-band at 576 nm with 4F9/2 -> 6H13/2 and bluish-band at 483 nm with 4F9/2 -> 6H15/2 transition. Firstly, luminous intensity of trivalent dysprosium ion rises and then decreases, this was because of quenching of concentration (CQ). The dipole-dipole interaction between the nearest dopant ions is responsible for this concentration quenching. Bi-exponential fitting behaviour in the focused nanophosphors confirms that there are two coordinatively different luminous centres are present in the host material for the incoming dopant ions. The luminescence decay lifetime for 4F9/2 energy level was found to be around 1.522 ms for the optimized phosphor composition. The value of integrated Y/B ratio for the samples being close to one, they can be promising candidate for white light emitting nanophosphors. The obtained outcomes authenticate the ability of Y4Al2O9:Dy3+ nanophosphor to be utilized in WLED's and other lighting appliances.