Synthesis and up-conversion luminescence properties of Ho3+, Yb3+ co-doped BaLa2ZnO5

• Up-conversion phosphors BaLa2ZnO5 co-doped with Ho3+/Yb3+ were synthesized.
• The crystal structure of BaLa2ZnO5 and the changes of cell parameters and volume of BaLa2ZnO5 after doping Ho3+ and Yb3+ have been discussed.
• The luminescence properties of BaLa2ZnO5 co-doped with Ho3+/Yb3+ were excellent.
• Energy transfer between Yb3+ and Ho3+ in BaLa2ZnO5 has been discussed.

Up-conversion phosphors BaLa2ZnO5 co-doped with Ho3+/Yb3+ were synthesized by high temperature solid-state reaction method. The phase composition of the phosphors was characterized by X-ray diffraction (XRD). The structure of BaLa2ZnO5: 0.75% Ho/15% Yb phosphor was refined by the Rietveld method and results showed the decreased unit cell parameters and cell volume after doping Ho3+ and Yb3+, indicating Ho3+ and Yb3+ have successfully replaced La3+. Under the excitation of 980 nm diode laser, the strong green and weak red up-conversion emissions centered at 548 nm, 664 nm and 758 nm were observed, which originating from 5S2, 5F2→5I8, 5F4→5I8 and 5S2, 5F2→5I7 transitions of Ho3+ ions, respectively. The optimum doping concentrations of Ho3+ and Yb3+ were determined to be 0.75% and 15%, and the corresponding Commission International de L'Eclairage (CIE) coordinates are calculated to be x=0.298 and y=0.692. The related UC mechanism of Ho3+/Yb3+ co-doped BaLa2ZnO5 depending on pump power was studied in detail. The results indicate that BaLa2ZnO5: Ho3+/Yb3+ can be an effective candidate for up-conversion yellowish-green light emitter.