Laser excitation‐activated self‐propagating sintering of NaYbF 4 :Pr 3+ /Gd 3+ white light microcrystal phosphors

• Published in: Journal of the American Ceramic Society 2019-04, Vol.102 (4), p.1814-1821
• Main Authors: Jiang, Mengci, Shen, Si, He, Jiayang, Wu, E, Zeng, Heping
• Format: Article
• Language: English
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.16043

We demonstrate that self‐propagating sintering reaction could be activated and dramatically enhanced by laser excitation of ion dopants in the solid‐state reactants. Near‐resonant laser absorption and subsequent nonradiative decays make the solid‐state reactants be sintered efficiently while ionic excitations catalyze self‐propagating solid‐state reactions. As a prototype demo, we synthesized white light upconversion phosphors NaYbF 4 :Pr 3+ /Gd 3+ . A continuous‐wave laser at 980 nm was used to populate Yb 3+ ions in YbF 3 to excited level, which react with NaF to preform NaYbF 4 nuclei. The preformed nuclei enhanced laser excitation and energy transfer to those ions that could not be directly excited by the pump laser and thus enabled self‐propagating solid‐state sintering synthesis of NaYbF 4 microcrystals at quite low laser powers. Laser excitation of Yb 3+ ions could also benefit facile rare‐earth ion doping through activated self‐propagating reactions. Gd 3+ and Pr 3+ ions were doped in NaYbF 4 by simply adding Gd 3+ and Pr 3+ ionic oxides or fluorides in the raw materials. In addition, Gd 3+ ions doping in F − anions ambient could transform the NaYbF 4 microcrystal phase from cubic to hexagonal and tune upconversion photoluminescence. This synthetic method can be widely applied to synthesize many other solid‐state compounds, perovskite solar cells, photocatalysts, solid oxide fuel cells, and so forth.