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 ∼110 to ∼2 μm, 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 ∼100 nm and ∼2 μm 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 (∼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.