Oxynitride K₂Ba_6.72Si₁₆O_40-1.5yN _y: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 K2Ba6.72Si16O40-1.5yNy:0.28Eu(2+) were synthesized by introducing N3- (y) into a K2Ba6.72Si16O40:0.28Eu(2+) 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 (epsilon(c)) and splitting of the 5d energy level (epsilon(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, K2Ba6.72Si16O31N6:0.28Eu(2+), benefits from an increased activation energy and thermal stability.