Bright orange upconversion in a ZnO–TiO2 composite containing Er3+ and Yb3+

• A novel bright orange up-conversion phosphor, ZnO–TiO2:Er3+, Yb3+ was developed.
• Brightest UC was observed in 1ZnO:1TiO2 composition containing 2 at.% Er and 6 at.% Yb.
• Optimum sintering temperature was about 1200–1250 °C for 4 h in air ambient.
• Brightest sample contained Zn2TiO4, TiO2 and RE2Ti2O7 mixed phases.
• Excess Ti4+ generates vacancies and traps responsible for enhancing the UC.

ZnO–TiO2 composite system containing Er3+ and Yb3+ were prepared by solid state reaction method and its upconversion (UC) luminescence excited by 980 nm laser was studied for the first time. The effects of firing temperature, ZnO/TiO2 composition and Er3+, Yb3+ concentrations on the UC emission behavior were examined. The ZnO–TiO2 composite product sintered at 1200 °C contained Zn2TiO4, TiO2 and RE2Ti2O7 (RE = Er3+ and Yb3+) phases and exhibited strong green and red emissions arising due to the 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions for Er3+ ion, respectively. Bright orange color by the mixing of green and red colors was observed in the 1ZnO–1TiO2 product doped with 2 at.% Er3+ and 6 at.% Yb3+. The ZnO–TiO2:Er3+, Yb3+ phosphor was compared to the brightest available phosphor, Y2O3:Er3+, Yb3+ and found to be 3-fold brighter than it. It suggests that ZnO–TiO2:Er3+, Yb3+ is a potential material for the orange upconversion phosphor.

The UC luminescence spectra of 1ZnO–1TiO2 mixture doped with 2 mol% Er3+ and 6 mol% Yb3+ sintered at various temperatures under excitation of a 980 nm cw laser. Inset shows the optical pictures of the corresponding samples.Figure optionsDownload high-quality image (56 K)Download as PowerPoint slide