Micronization of red-emitting K2SiF6:Mn4+ phosphor by pulsed laser irradiation in liquid

We demonstrate a technique for the micronization of K2SiF6:Mn4+ phosphor particles by pulsed laser irradiation in liquid. Through nanosecond pulsed laser irradiation in liquid, the average diameter of the phosphor particles dramatically decreases from similar to 110 to similar to 2 mu m, and the extent of decrease depends on the wavelength of irradiated laser light. This is due to the wavelength dependence of phosphor absorbance. A bimodal size distribution peaked at similar to 100nm and similar to 2 mu m is also observed, indicating the coexistence of several different fragmentation mechanisms: shockwave, thermal-stress, and heating evaporation fragmentations. The micronized phosphor particles still exhibit red emission but show lower photoluminescence quantum efficiency (similar to 0.2) than that without micronization. This lower efficiency is caused by the increase in the nonradiative recombination channels, which is probably due to the formation of the internal and/or surface defects. (C) 2014 Elsevier B.V. All rights reserved.