Preparation and upconversion properties of Yb3+, Ho3+: LU2O3 nanocrystalline powders

Yb3+, Ho3+ : Lu2O3 nanocrystalline powders were synthesized by a reverse-strike co-precipitation method using NH4HCO3 and NH3 (.) H2O as precipitators. X-ray diffraction analysis and field emission scanning electron microscopy observation showed that the phase composition of the powders was cubic and the particle size was 30-50 nm. Under the excitation of a 980 nm continuous wave diode laser, green and red emissions centered around 548 and 667 nm, respectively, were observed and the green emission dominated the upconversion spectrum. Power studies revealed that a two-photon process was involved in the upconversion emissions and the possible upconversion mechanisms were discussed.