Photoluminescence and structural analysis of trivalent europium doped MLaAl₃ O₇ (M = Ba, Ca, Mg and Sr) nanophosphors

The solution combustion technique was used to synthesize MLaAl₃ O₇ (M = Ba, Ca, Mg, and Sr) nanophosphors-doped with Eu³⁺ using metal nitrates as precursors. The photoluminescence (PL) emission spectra exhibited three peaks at 587-591, 610-616, and 653-654 corresponding to ⁵ D₀ →⁷ F₁ , ⁵ D₀ →⁷ F₂ , and ⁵ D₀ →⁷ F₃ transitions, respectively. Upon excitation at 254 nm, these nanophosphors displayed strong red emission with the dominant peak attributed to the ⁵ D₀ →⁷ F₂ transition of Eu³⁺ . The materials were further heated at 900 and 1050°C for 2 h to examine the consequence of temperature on crystal lattice and PL emission intensity. X-ray diffraction (XRD) analysis proved that all the synthesized materials were of a crystalline nature. CaLaAl₃ O₇ material has a tetragonal crystal structure with space group P421m. Scherer's equation was used to calculate the crystallite size of synthesized phosphors using XRD data. A Fourier transformation infrared study was used to observe the stretching vibrations of metal-oxygen bonds. Infrared peaks for stretching vibrations corresponding to lanthanum-oxygen and aluminium-oxygen bonds were found at 582 and 777 cm^-1 respectively for CaLaAl₃ O₇ phosphor material. Transmission electron microscopy images were used to determine the size of particles (18-37 nm for the as-prepared materials) and also to analyze the three-dimensional view of these materials. The experimental data indicate that these materials may be promising red-emitting nanophosphors for use in white light-emitting diodes.