Synthesis and optical studies of nanocrystalline Eu2+-doped and RE3+(Nd3+, Dy3+)-codoped Ba4Al14O25 materials for UV-LEDs

Abstract Green emitting Ba4Al14O25:Eu2+ and Ba4Al14O25:Eu2+,RE3+ (RE3+ = Nd3+, Dy3+) phosphors for ultraviolet light emitting diodes (UV-LEDs) were prepared via combustion technique at 600 °C. The as-prepared samples were reheated at 1150 (2 h) and 1350 °C (6 h) in a tube furnace under reducing condition (95 % dinitrogen and 5 % dihydrogen). The photoluminescence emission (PL) spectra were recorded to examine the effect of temperature and presence of codopants on the luminescence properties of materials. On excitation at 362 nm, PL spectra of these phosphors exhibited intense band at 480−520 nm due to spin-allowed 4f65d1→4f7 transition in Eu2+. The luminescence intensity and persistence behaviour of materials was improved in presence of Nd3+ and Dy3+ ions as codopants. The diffraction analysis confirmed the synthesis of lattice having orthorhombic structure with Pmma symmetry. The crystalline nature of samples was found to be increased at higher temperature. Transmission electron microscope (TEM) images exhibited that the prepared materials have nearly spherical shape in nano-range. The structure and chemical bonding of materials were supported by Fourier transform infrared (FTIR) spectra.