Structural, morphological, and optical characteristics of Gd₂ Si₂ O₇ :Dy³⁺ nanophosphors for WLEDs

Yellowish-white light-emitting Gd_2-x Si₂ O₇ :xDy³⁺ (x = 1-5 mol%) nanophosphors were prepared using a solution combustion synthesis method. Fluorescence spectrophotometry and X-ray diffraction measurements were performed to scrutinize the optical performances and phase recognition of the designated nanophosphors. The outcomes specified that the prepared phosphors were crystallized into a triclinic phase with a P-1 space group. As the concentration of Dy³⁺ ions was increased, the unit-cell volume decrease proportionally due to the replacement of large-sized Gd³⁺ by small-sized Dy³⁺ ions. Under ultraviolet excitation at 349 nm, emission spectra consisted of two pronounced emission lines at ~482 nm (blue line), ~578 nm (yellow line), and a relatively weaker emission at ~670 nm (red line) due to ⁴ F_9/2 →⁶ H_15/2 , ⁴ F_9/2 →⁶ H_13/2 , and ⁴ F_9/2 →⁶ H_11/2 intraconfigurational transitions of Dy³⁺ ions, respectively. The evidence about the site symmetry around Dy³⁺ ions was examined by considering the ratio of yellow-to-blue emission intensity. The observed critical distance (R_c ) value was ~20.56 Å (≫5 Å), which signified that energy transfer primarily occurred due to multipolar interaction. The obtained coordinates were close to the white region of the Commission Internationale de l'Éclairage chromaticity diagram, which marked a significant milestone in the development of white light-emitting diodes.