Oxynitride K₂Ba_6.72Si₁₆O_40-1.5N:0.28Eu²⁺ phosphor with high thermal stability realized by crystal field engineering

Extensive research has gone into modifying the chemical composition of phosphors to achieve desirable optical properties. Here, oxynitride phosphors K₂Ba_6.72Si₁₆O_40-1.5N:0.28Eu²⁺ were synthesized by introducing N^3- (y) into a K₂Ba_6.72Si₁₆O₄₀:0.28Eu²⁺ lattice. An uneven shrinking of the cell parameters a, b, and c was observed through a combination of X-ray diffraction studies and Rietveld refinements. This shrinking caused a large centroid shift (ε_c) and splitting of the 5d energy level (ε_cfs), thus inducing the broadening of the excitation spectra (104 → 127 nm, y = 0 → y = 12) and the red shift of the emission spectra (501 → 543 nm, y = 0 → y = 12). The modified series of samples have a broad excitation spectrum, suitable of use in UV, near-UV, and blue light-emitting LEDs. In addition, the optimal sample, K₂Ba_6.72Si₁₆O₃₁N₆:0.28Eu²⁺, benefits from an increased activation energy and thermal stability.