Synthesis of Eu-doped SrAl2O4 nanophosphors by CO2 laser vaporization

A new method of synthesizing spherical nanoparticles with photoluminescent spinel structures using a CO2 laser co-vaporization technique (CoLAVA) is presented. The method applies homogeneous mixtures of oxidic precursors such as Al2O3, SrO and Eu2O3 and allows the fabrication of quantities exceeding 10 g h−1. During the CoLAVA process, the educt oxides are reacted by a gas phase condensation yielding amorphous spherical particles with diameters ranging from 10 to 100 nm. The as-prepared materials exhibit red emission at 625 nm (1.98 eV) due to the incorporated Eu3+. Temperature treatment up to 1200 °C under a reducing atmosphere yielded crystalline particles of the same size, which were slightly sintered. These particles consisted of >90 wt.% SrAl2O4 with minor fractions of Sr3Al2O6 and SrCO3. The amount of the SrAl2O4 spinel increased with increasing temperature, whereas the accompanying phases were decreased. A strong green emission centered at 525 nm (2.36 eV) detected at RT was observed at an onset temperature of 900 °C, which is due to the presence of Eu2+ in the crystal lattice of SrAl2O4. The red emission was not observed at higher annealing temperatures. The CoLAVA method represents a fast and facile route for the fabrication of nano- to microstructured phosphor materials for a variety of engineering applications.