Transparent Ce,Sm:TAG Luminescent Ceramics for High Power Blue Laser Driven Lightning and Display Technologies

Abstract

Phosphor converted warm white light with high luminous efficacy and color-rendering index is crucial for the future of blue laser driven display technologies. Particularly in projection design where the high power (over 150 W) blue laser source is focused on the phosphor, the ideal phosphor candidate has to provide better conversion efficiency; longer lifetime (20000 hours) and lower thermal overheat. Conventional Ce:YAG suffers from efficient green and particularly red emission. Tb and Sm, known as green and red line emitters, respectively, can improve the color quality drastically. Ce, Sm: TAG ceramic powders were synthesized through spray pyrolysis from nitrate salts. Transparent ceramics has been produced via spark plasma sintering. Their phase compositions and structure parameters were checked by X-ray diffraction. The luminous properties of the transparent ceramics are improved when compared to the commercial phosphor wheels (Ce:YAG). Transparent ceramic exhibited broad emission with improved green and red region of the visible light compared to conventional Ce:YAG phosphor. Balanced Sm3+, Ce 3+admixture into the TAG lattice provided excellent color coordinates and CRI for the phosphor for warm white light illumination. Optical and luminescence characteristics were investigated throughout absorbance, excitation and, emission spectra with temperature dependence. Luminous efficacy over 250 lm/W with correlated color temperature (CCT) ~3800 K, color rendering index (CRI) >80 are achieved. The high-power blue diode laser driven temperature increase versus luminous efficacy and quantum efficiency is discussed. The results indicate that Ce, Sm:TAG transparent ceramics can serve as potential phosphors candidates for high-power blue diode laser driven display technologies.