Synthesis and up-conversion properties of Er³⁺doped ZnTiO₃-Zn₂TiO₄composite phosphor

The conventional solid state reaction method was used to prepare Er3+ activated ZnTiO3-Zn2TiO4 composite phosphor. The structure, particle morphology, absorption, and photoluminescent properties were analyzed using x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis-NIR absorption spectrometer, and photoluminescence (PL) spectroscopy, respectively. The XRD confirmed the crystallization of mixed hexagonal ZnTiO3 and cubic spinel Zn2TiO4 phases. The SEM data showed that the prepared phosphor was made up of faceted hexagons. Furthermore, the phosphor was excited in the near-infrared (NIR) region using a laser diode with a wavelength of 980 nm, and the corresponding up-conversion emission lines were observed in the visible range at 543, 553, and 650-670 nm, associated with the 2H11/2 → 4I15/2, 4S1/2 → 4I15/2, and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. The interaction mechanisms involved in the up-conversion process of ZnTiO3-Zn2TiO4:Er3+ phosphor are discussed with the help of an energy-level schematic diagram, and the number of the photons involved in the up-conversion luminescence process was estimated.