Efficient Sr0.5Ca0.5AlSiN3:Eu2+ red-emitting ceramics for high-power solid-state lighting

Solid-state lighting is now developing toward high-power and super-brightness, but is largely limited by the lack of highly robust and efficient color conversion materials that can be survived from high-power or high-power density excitation, typically the red-emitting ones. In this work, we fabricated highly efficient and pore-free Sr0.5Ca0.5AlSiN3:Eu2+ (SCASN) red-emitting ceramics by spark plasma sintering of fine phosphor powders. These fine phosphor powders were prepared by treating the commercial phosphors with high-energy ball-milling, centrifugation and acid washing, leading to a particle size of 2.55 μm and an internal quantum efficiency as high as 74.0% under 450 nm excitation. The phosphor powders can be densified into SCASN ceramics without using sintering additives at a temperature as low as 1475 °C, and the ceramics show an internal quantum efficiency of 75.3%, which is 50% higher than those ceramics fabricated with untreated commercial powders. When excited by a high-power blue LED at a current density of 4 A/mm2, the SCASN ceramics have a maximum luminous flux of 660 lm (i.e., 26 Mcd/m2). The phosphor ceramics can also withstand a high laser power density of 15.7 W/mm2, and exhibit an output luminance of 188 Mcd/m2. This work provides a general method to prepare fine phosphor powders that enable to fabricate high efficiency phosphor ceramics used in high-power solid-state lighting.