Divalent ytterbium-doped Ca-α-SiAlON phosphors were synthesized by a spark plasma sintering (SPS) method without a reducing gas. A single phase Ca-α-SiAlON:Yb 2+ was successfully achieved at relatively low temperature of 1600°C. Its photoluminescence excitation spectrum showed a broad band peaking at 450nm due to the 4f 13 5d 1 →4f 14 transition of Yb 2+ ions, while a corresponding green emission band was observed at 545nm. The post-annealing in a reduced atmosphere significantly improved the luminescent properties by increasing the crystallinity, reducing the carbon contamination, and changing the residual Yb 3+ to Yb 2+ in as-synthesized samples. The post-annealed powders, compared to commercial YAG:Ce 3+ and silicate phosphors, showed a low thermal quenching due to the rigid crystal structure.