Polymer-derived preparations of the blue-excited greenish-yellow-emitting calcium-containing ?-Si3N4:Eu-like phosphors

Polymer-derived greenish-yellow emitting silicon (oxy)nitride phosphors excited by blue light were prepared by using polycarbonsilane, europium (Eu) and calcium (Ca) acetylacetonates as raw materials. The chemical compositions, crystal phases, particle morphologies and microstructures of the samples prepared with Eu, and/or Ca, and none of any metal ions were studied and are compared. It was found that the Ca-containing Eu-activated silicon (oxy)nitride sample prepared with the atomic ratios of Eu/Si and Ca/Si being 0.06 and 0.12, respectively, was composed mainly of single crystallized particles in the ?-Si3N4-like phase with Eu2+/3+ and Ca2+ ions locating at interstices of the ?-Si3N4-like lattices. This sample demonstrated a substantial increment in the intensity of its broad and spike-less emission spectrum excited at 468 nm as compared to that for the Ca-free sample with its major emission peak being at 570 nm, and recorded a CIE coordinate (0.3386, 0.3474) near the equal energy white point with a Ra value of 71.4 when employed as the phosphor for a white light emitting diode device with blue chip of 460 nm. The emission mechanisms of Eu-activated for the Ca-free sample and the Ca-containing sample, the later res-shifted the major excitation band from the near-ultraviolet to blue, are discussed based on the experimental data.

Automated summary

Polymer-derived greenish-yellow emitting silicon (oxy)nitride phosphors were prepared with specific raw materials, leading to controlled and enhanced emission spectra. The Ca-containing Eu-activated silicon (oxy)nitride sample demonstrated stronger luminescence under blue light excitation, showing potential for application in white light emitting diode devices.