Solid state diffusion and amalgamating anionic exchange at a KNaSO₄ phosphors activated with Eu³⁺ , Dy³⁺ and Sm³⁺...

In present work, KNa(SO₄ ) phosphors doped with different concentrations of rare earth Eu³⁺ , Sm³⁺ and Dy³⁺ ions (0.05, 0.1, 0.3, 0.5, 0.7, 1 mol%) were synthesized using a solid-state diffusion technique. Photoluminescence (PL) investigations were carried out for the whole range of Eu³⁺ , Sm³⁺ and Dy³⁺ -doped phosphors; rare earth ions that retained maximum PL intensity were selected for advanced anionic exchange. In the present investigation, phosphors KNa(SO₄ ):Eu³⁺ (1 mol%), KNa(SO₄ ):Dy^3 +  (0.5 mol%) and KNa(SO₄ ):Sm³⁺ (0.3 mol%) had the highest PL intensity, and were therefore selected for further anionic substitution of sulphate anions with different concentrations of vanadate, phosphate, and tungstate anions, such as KNa(SO₄ )_1-x (MO₄ )_x : W (where W = Eu³⁺ 1 mol%, Dy³⁺ 0.5 mol% and Sm³⁺ 0.3 mol%; MO₄  = PO₄ , VO₄ , WO₄ ; and x = 0.1, 0.3, 0.5, 0.7, 1). Structural and molecular environments of the substituted phosphors were characterized individually using X-ray diffraction and Fourier transform infrared spectroscopy. In-depth morphological investigations of the prepared phosphors were undertaken using scanning electron microscopy. For the principal investigation on enhancement of white light-emitting diode (w-LED) performance, the PL properties of all the synthesized phosphors were studied analytically. Emission intensity ratios for KNa(SO₄ ):Eu³⁺ 1 mol%, KNa(SO₄ )₀ (PO₄ )₁ :Eu 1 mol%, KNa(SO₄ )_0.9 (VO₄ )₁ :Eu 1 mol%, and KNa(SO₄ )_0.9 (WO₄ )_0.1 :Eu 1 mol% were 1:1.15:1.23:0.08. PL intensity ratios for the phosphors KNaSO₄ :Dy 0.5 mol% and KNa(SO₄ )_0.9 (PO₄ )0.1:Dy 0.5 mol% was 1:2. The ratio of PL intensity was 1:3.2:0.8 for KNa(SO₄ ):Sm 1 mol%, KNa(SO₄ )_0.5 (PO4)_0.5 :Sm 0.3 mol%, and KNa(SO₄ )_0.7 (VO₄ )_0.3 :Sm 0.3 mol% phosphors, respectively. Chromaticity investigations were carried out using Commission Internationale de l'Éclairage colour co-ordinate diagrams, which suggested that the prepared Eu³⁺ -doped and Sm³⁺ -doped phosphors would be prospective candidates for red and green LEDs, respectively, whereas Dy³⁺ -doped phosphors showed emission in the blue and yellow regions. The entire study indicated that amalgamation of anionic exchange at a KNaSO⁴ phosphor activated with Eu³⁺ , Dy³⁺ and Sm³⁺ rare earth ions could generate and enhance white light emission.