Strong infrared-to-visible frequency upconversion in Er3+-doped Sr2CeO4 powders

Efficient upconversion (UC) luminescence is demonstrated in Er3+:Sr2CeO4 powders prepared by combustion synthesis and exposed to near-infrared (∼975 nm) radiation. The UC emission lines observed at ∼530, ∼550 and ∼665 nm correspond, respectively, to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 4f–4f transitions of Er3+. X-ray powder diffraction data showed that the SrCO3 phase (impurity) is dramatically reduced when Sr2+ is partially substituted by Mg2+ ions. The UC phenomenon was investigated by use of continuous wave and pulsed laser excitation and the UC mechanism was attributed to energy transfer between excited Er3+ ions.