Highly stable red oxynitride β-SiAlON:Pr³⁺ phosphor for light-emitting diodes

Trivalent Pr³⁺-doped oxynitirde red phosphors β-SiAlON with composition Si_6-zAl_zO_zN_8-z:Pr _x (z = 0-2.0, x = 0.016) were synthesized by gas pressure sintering (GPS) at 1950 °C for 2 h. Red luminescence in the range 600-650 nm was detected upon excitation with 460 nm blue light, indicating that the phosphor can be excited by blue InGaN light-emitting diodes (LED). The crystallization and cell parameters of samples were investigated by powder X-ray diffraction (XRD), Rietveld refinement, and high-resolution transmission electron microscopy (HRTEM). Energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) were further adopted to examine the effect of Al substitution on the microstructure. ²⁷Al and ²⁹Si solid-state nuclear magnetic resonance (NMR) data are consistent with SiN_4-xO_x and partially substituted AlN_4-xO_x tetrahedra. The temperature-dependent luminescence from the ¹D₂ and ³P₀ states of Pr³⁺ were studied (10-573 K), and the integrated red emission from 600 to 650 nm increased with temperature (298-473 K). This unexpected phenomenon is proposed to be the result of two crossed excitation states in the configurational coordination diagram. This investigation reveals the superior characteristics of nitride compounds and the feasibility of doping Pr³⁺ into phosphor.