SrWO4:Er3+/Yb3+ nanorods: Synthesis and upconversion luminescence

SrWO4:Er3+/Yb3+ nanorods are synthesized by the hydrothermal process with the addition of CTAB. The phase, morphology, size and upconversion luminescence are characterized. The XRD patterns indicate that SrWO4:Er3+/Yb3+ samples belong to the scheelite-type tetragonal structure with space group I41/a. The TEM results show that SrWO4:Er3+/Yb3+ nanorods have the diameter about 50 nm and the length about 200 nm. Under the excitation at 980 nm, SrWO4:Er3+/Yb3+ emit green and red emissions originating from 2H11/2, 4S3/2 → 4I15/2 and 4F7/2 → 4I15/2 transitions of Er3+ ions. The intensities of green and red emission have close relation with the concentrations of Er3+ and Yb3+ ions. For Er3+ single doped SrWO4 samples, both green and red emission intensities increase with the increasing concentration. For Er3+ and Yb3+ codoped SrWO4 samples, the ratios of red emission to green emission increase with the increasing concentrations of Yb3+ ions. On the basis of the luminescence properties of SrWO4:Er3+/Yb3+ samples, we can conclude that two-photon process is responsible for green and red emissions.