Synthesis and upconversion luminescent properties of Er3+ doped and Er3+–Yb3+ codoped GdOCl powders

Er3+ doped and Er3+–Yb3+ codoped GdOCl phosphors were prepared by modified solid state reaction. X-ray diffraction, scanning electron microscope, and Raman spectrum of the samples were studied. The result of Raman spectrum shows that the cutoff phonon energy of GdOCl is only 505 cm−1, which is beneficial for upconversion luminescence. Infrared-to-visible upconversion emissions were observed under 980 nm diode laser excitation. It was found that the ratio of green to red upconversion emission intensity varies with concentration of the Er3+ or Yb3+ ion. Laser power and doping concentration dependence of upconversion luminescence were studied to understand the upconversion mechanisms. Excited state absorption and energy-transfer processes are proposed to be the possible mechanisms for the visible emissions.

► Synthesis of Er3+ and Er3+–Yb3+ doped GdOCl powders by solid state reaction. ► The phonon cutoff energy of GdOCl is only 505 cm–1. ► The Er3+ or Yb3+ concentration has significant influence on upconversion spectra. ► The green and red emissions originate from a two-photon upconversion process. ► Upconversion mechanism consists of excited state absorption and energy transfer.