Synthesis and photoluminescence characterisation of Ca2La2O5:Eu3+, a novel red-emitting phosphor: a comprehensive study

Abstract

ABSTRACT A novel low-melting-temperature chemical flux method was used to synthesise a Ca2La2O5 lattice doped with Eu3+ ions in the range of 0.5-2.5 mol-%. The phosphors were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, particle size distribution, photoluminescence (PL), and Fourier transform infrared spectroscopy, respectively. The PXRD pattern revealed the hexagonal crystal structure with the space group P63/m. The microstrain (ϵ) was found to not vary with different concentrations of dopant and the negative means compression in the lattice. Particles of varying sizes and irregular shapes were observed from the SEM micrographs. The EDAX mapping revealed that all the constituent elements were found to be in appropriate ratios. Interestingly, the Ca2La2O5:xEu3+ (x = 0.5-2.5 mol-%) phosphor samples were excited at 590 nm, showing a Stokes-shifted red-PL with significant intensities at 615 and 627 nm. Unconventionally, when the phosphor is excited at 590 nm, the Eu3+ ion-characteristic luminescence owing to 5D0→7FJ (J = 0, 1, 2, 3, 4) transitions are manifested. Another remarkable observation is that the PL at 627 nm corresponding to 5D0→7F3 transition was much stronger than the 615 nm emission of Eu3+ corresponding to 5D0→7F3 transition, indicating high colour purity among the available red-emitting phosphors.