No abstract

CP because it can be achieved white light directly combined with blue LDs. [19][20][21][22][23] Recently, yellow/green/red CPs were discovered to rich spectral components and modify the color quality for white LD lighting. [24][25][26][27][28] Lu 3 Al 5 O 12 :Ce (LuAG:Ce) is a well-known green color converter due to its high thermal stability and high efficiency. [29][30][31] LuAG:Ce CPs are regarded as the best type that is robust irradiated by high-power LD light (15-25 W, up to 49 W mm −2 ). [32][33][34][35][36] The luminous efficacy (LE) of LuAG:Ce CPs in LD lighting has been greatly enhanced from about 54 to 205 lm W −1 by designing geometric structures and introducing scattering centers. [32][33][34][35][36][37] However, LuAG CPs are usually sintered higher than 1700 °C, SiO 2 or TEOS is commonly added as sintering aid. [32][33][34] SiO 2 begins to react with the garnets at about 1400 °C, [38] and defects are inevitable due to the size and charge mismatches between Si 4+ and Lu 3+ /Al 3+ . [39] The defects decline the thermal stability that is directly related with the performance of LuAG:Ce in LD lighting. [19] Thus, how to depress the defect and maintain the high thermal stability is the hardest challenge in fabricating LuAG CPs and achieving high LE value.As we know, heavy atom can depress lattice relaxation and improve thermal stability. [40,41] Considering valence state, in this work, we design the Ba 2+ -Si 4+ pair to substitute the Lu 3+ -Al 3+ pair to keep charge balance. SiO 2 powder are used as sintering aid and BaCO 3 provides the Ba 2+ to control defects and adjust thermal stability. Combining annealing process in air to eliminate oxygen vacancies, LuAG:Ce CPs manifest high LE of 213.7-216.9 lm W −1 in LD lighting, which is the best performance up to date. These results demonstrate that suitable strategies further improve LuAG:Ce CPs properties, thus in turn making great contributions to high-brightness and efficient white LD lighting. The tunable thermal stability by Ba 2+ -Si 4+ pairs and relationships with performance of LuAG:Ce CPs in LD lighting are detailed in present report. Results and DiscussionNominal compositions of Lu 2.995−x Ba x Al 5−x Si x O 12 :0.005Ce (LuAG:0.5%Ce+xBS, x = 0, 0.005, 0.01, 0.015, and 0.02) CPs sintered in vacuum are dark yellow (unannealed samples in Figure 1a), especial for x = 0, due to a lot of color centers Lu 3 Al 5 O 12 :Ce 3+ (LuAG:Ce 3+ ) ceramic phosphors (CPs) are regarded as the most promising green color converter and play a key role in high quality white light in the next-generation laser diode (LD) lighting. High efficient LuAG:Ce 3+ CPs are still urgent for high luminous efficacy (LE) LD lighting devices. By designing the Ba 2+ -Si 4+ pair to keep charge balance and annealing in air to remove oxygen vacancy defects, the luminescent properties of LuAG:Ce CPs are greatly enhanced. The LE is promoted to 216.9 lm W −1 , which is the best performance of LuAG:Ce in LD lighting so far. Strategies for optimizing LuAG:Ce 3+ CPs are detailed. It is believed ...

No abstract