Influence of Er3+/Yb3+ concentration ratio on the down-conversion and up-conversion luminescence and lifetime in GdVO4:Er3+/Yb3+ microcrystals

In this paper, we studied the effects of Er3+/Yb3+ concentration ratio on structural, morphological and luminescence properties of GdVO4:Er3+/Yb3+ green phosphors prepared by a high-temperature solid state method. The samples with different concentrations (between 0.5 to 2 mol%) of dopant Er3+ emitting ions and different concentrations (between 5 to 20 mol%) of sensitizer ions (Yb3+) were studied. The phosphors were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy. For all samples, XRD diffraction patterns confirmed a formation of a pure GdVO4 phase, while the SEM showed that the materials are comprised of chunks of deformed particles with an average diameter ranging from approximately 2 ?m to 8 ?m. Both, down-conversion and up-conversion emission spectra of GdVO4:Er3+/Yb3+ samples, under near UV and IR excitations, exhibit two strong emission bands in the green spectral region at 525 nm and 552 nm wavelengths corresponding to 2H11/2 ?4I15/2 and 4S3/2 ? 4I15/2 electronic transitions of Er3+ ions. The intensity of the green emission was changed by changing the Er3+/Yb3+ concentration ratio. This dual-mode luminescence makes these materials ideal as green phosphors for a wide variety of applications in the fields of bioanalysis and biomedical.

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