Longcheng Wang

CONTROLLED SYNTHESIS OF CU2O MICRO-CRYSTALS WITH VARIOUS MORPHOLOGIES BY ADJUSTING SOLUTION CONDITIONS

Micro-crystals of cuprous oxide with different morphologies were prepared by a hydrothermal process with copper sulfate and sodium lactate as precursors. Morphology of cuprous oxide was simply controlled by adjusting solution pH values or addition of different amounts of organic solvent. Structural properties of all the samples were characterized by X-ray diffraction and scanning electron microscopy. The growth mechanism of cuprous oxide micro-crystal under different conditions was discussed. Results show that morphologies of cuprous oxide micro-crystals alter from branched structure to octahedron structure and cube structure with growth conditions.

Study on the oxygen exchange capacities of Ce2Sn2O7 pyrochlore

Ce2Sn2O7 pyrochlore was synthesized by a hydrothermal method. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composition and valence state of the sample. The oxygen exchange property of the Ce2Sn2O7 phase was measured by an oxidation reaction in sealed air atmosphere and a followed reduction reaction in 5% H2-95% N2 atmosphere. Gas chromatography (GC) was used to analyze the oxygen change in the reaction. The results show that Ce2Sn2O7 sample has excellent oxygen absorption capacity at 250°C as Ce3+ ions are oxidized to Ce4+ ions. The oxidized sample can be reduced by 5% H2-95% N2. The refreshed sample remains the capacity of oxygen absorption, while the oxygen exchange capacity degrades with the reduction times.

Study of the effect of Li+ concentration on the photoluminescence properties of Y2O3:Eu3+ phosphors

Y2O3:Eu3+ phosphors were prepared by hydrothermal method. Effect of the doping concentration of Eu3+ on the photoluminescence properties of Y2O3:Eu3+ phosphor was studied in details. It was found that the strongest emission intensity is achieved as atomic ratio of Y3+ to Eu3+ is 8. As concentration of Eu3+ exceeds the critical concentration, the emission intensity decreases dramatically due to the concentration quenching of Eu3+. Also, the effect of Li+ on the photoluminescence performance of the Y2O3:Eu3+ phosphor is studied in this work. According to the results, the doping of Li+ may greatly improve the PL performance of the Y2O3:Eu3+ phosphors due to the flux effect and improved crystallinity caused by the doping of Li+.