Enhanced red luminescence and improved crystallinity in NaEu(WO4)2 phosphors: an electron beam irradiation study

Abstract

A sodium Europium Double Tungstate (NaEuW) red phosphor was synthesized by a facile hydrothermal method and characterized by powder XRD, FTIR, UV-DRS, FESEM and photoluminescent measurements. The influence of different doses of high energy electron beam (EB) irradiation on the structural, morphology and fluorescence properties of NaEuW crystallizing in the I4₁/a space group was investigated for the first time in comparison with non-irradiated NaEuW. Different doses of high energy EB irradiation resulted in a systematic shift in the diffraction peaks towards lower 2θ, indicating unit cell volume expansion. Interestingly, phase purity was retained even at a higher EB dose, signifying the structural stability of the NaEuW red phosphor. An insight into the FESEM micrographs shows improved crystallinity and agglomeration upon EB irradiation. The resultant NaEuW phosphor emits bright red color under UV excitation of wavelength 396 nm and the intensity was significantly varied for different doses of EB irradiation. At an optimum dose of 20 KGy, a very high color purity was obtained from the calculated CIE-X and Y of the CIE chromaticity diagram of the irradiated NaEuW samples. Additionally, the CIE-X and CIE-Y coordinates of the irradiated material are observed to be closer to the commercially available red phosphor Y₂O₃S:Eu³⁺. Hence, this work could present a potentially new strategy to improve the fluorescence properties of phase pure NaEuW via EB irradiation.