Investigation of the photoluminescence studies of ZnO: Dy³⁺ nanophosphors via different anionic group (BO₃³⁻, PO₄²⁻, and SO₄²⁻) substitutions

A series of ZnO-SG: xDy³⁺ (x = 1 mol % and SG = BO₃³⁻, PO₄²⁻, and SO₄²⁻) phosphors were successfully synthesized through chemical combustion synthesis. The prepared phosphors were characterized by different characterization techniques such as x-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Ultraviolet-Visible spectroscopy (UV–vis), x-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy, to study their crystal, morphological, optical, surface, and luminescent properties. The analysis of XRD patterns revealed that ZnO, ZnO: Dy³⁺, and ZnO-SO₄:Dy³⁺ crystallize in a ZnO hexagonal wurtzite crystal structure; however, for the borate and phosphate, there was a change of crystal structure to a Zn₄B₆O₁₃ cubic and Zn₂P₂O₇ monoclinic crystal structure, respectively. The EDS analysis of the prepared materials revealed the presence of all elements, and no unexpected peaks were observed. This was further confirmed by XPS surface analysis, which also revealed the oxidation states of the elements in these materials. Three PL characteristic emissions of Dy³⁺ in the visible region with high intensities were observed for the borate and phosphate materials, which was not the case for the other samples. The three observed emissions at 484 nm, 575 nm, and 664 nm were attributed to Dy³⁺ transitions from ⁴F_9/2 to ⁶H_15/2 ⁶H_13/2, and ⁶H_11/2 levels, respectively. A structural change has resulted in a shift from the orange-emitting phosphor material ZnO, which has a 93% colour purity, to yellow-emitting phosphor materials with colour purities of 88%, 78%, and 99% for ZnO-SO₄:Dy³⁺, Zn₄B₆O₁₃:Dy³⁺, and Zn₂P₂O₇:Dy³⁺, respectively.