Precipitation of Eu 3+ - Yb 3+ Codoped ZnAl 2 O 4 Nanocrystals on Glass Surface by CO 2 Laser Irradiation

We present a novel and simple method to enable spatially selective ZnAl2O4 nanocrystal formation on the surface of B2O3-Al2O3-ZnO-CaO-K2O glass by employing localized laser heating. Optimized precipitation of glass-ceramics containing nanocrystals doped with Eu3+ and Yb3+ ions was performed by controlling CO2 laser power and scan speed. Micro-x-ray diffraction and transmission electron microscopy revealed the mean size and morphology of nanocrystals, and energy dispersive x-ray spectroscopy showed the lateral distribution of elements in the imaged area. Laser power and scan speed controled annealing temperature for crystalization in the range of 1.4-1.8 W and 0.01-0.3 mm/s, and changed the size of nanocrystals and distribution of dopant ions. We also report more than 20 times enhanced downshift visible emission under ultraviolet excitation, and 3 times increased upconversion emission from Eu3+ ions assisted by efficient sensitizer Yb3+ ions in nanocrystals under 980 nm excitation. The confocal microscope revealed the depth profile of Eu3+ ions by showing their emission intensity variation.