Intrinsic red luminescence of Eu3+-activated lanthanum molybdate: Insights into the spectroscopic features using Judd–Ofelt theoretical analysis

Abstract

The spectroscopic properties of intense red-emitting La2-xEux(MoO4)3 nanophosphors synthesized by co-precipitation method were investigated on the basis of Judd–Ofelt theoretical analysis. The dominance of 5D0→7F2 electric dipole transition contributing the major part of red luminescence of the nanophosphors and the asymmetric site occupancy of Eu3+ ions was justified from the observed trend of Ω2 > Ω4 in the Judd–Ofelt intensity parameters. The major radiative parameters – especially fluorescence branching ratio, stimulated emission cross-section and gain bandwidth of the prominent Eu3+ transitions of nanophosphors – were derived from Judd–Ofelt intensity parameters and compared with the corresponding values reported in other Eu3+-doped host matrices. The relatively high values of radiative parameters of Eu3+ ions in the lanthanum molybdate host matrix and the experimentally measured quantum yield of about 45.23% substantiate the relevance of the prepared phosphor material. The possibility of NUV excitation of the material and the Mo–Eu energy transfer mechanism was established from the intense emission of Eu3+ ions upon host sensitization. The high color-purity red emission of the phosphor material with chromaticity co-ordinates (0.649, 0.348) – in close proximity to that of commercial Y2O3:Eu3+ and Y2O2S:Eu3+ red phosphors with CIE co-ordinates (0.645, 0.347) and (0.647, 0.343), respectively – corroborates the significance of La2-xEux(MoO4)3 nanophosphors as efficient red emitters.