Photoluminescence tuning of Na_1−xK_xNdW₂O₈ (0.0 ≤ x ≤ 0.7) nanoparticles: synthesis, crystal structure and Raman study

Abstract

A series of Na_1−xK_xNdW₂O₈ (0.0 ≤ x ≤ 0.7) nanoparticles have been synthesized by an efficient glycothermal technique for the first time. SEM measurements confirmed the particle size ranges from 30–200 nm with ellipsoidal shaped morphology. Combined X-ray and neutron diffraction and Raman spectroscopy techniques were utilized in order to investigate the influence of K⁺ ion substitution in NaNdW₂O₈. K⁺ ion substitution in the crystal lattice introduced a change in the Nd–O bond length and the Nd–O–W bond angle of NaNdW₂O₈. The photoluminescence intensity increased up to the threshold composition x = 0.4. K⁺ ion substitution resulted in blue shifted emission of NaNdW₂O₈. Size mismatch, the Nd–O–W angle and local disorder contributed to the observed difference in luminescence properties. Also, the chromaticity diagram for this blue emitting phosphor showed the possibility of tuning the emission by incorporation of K.