Dejian Hou

Structure and luminescence properties of Sm 3+ doped Y 2 MoO 6 phosphor under near ultraviolet light excitation

Abstract A series of Sm 3+ doped Y 2 MoO 6 were prepared through high temperature solid state reaction technique. Their phase structures, morphologies and luminescence properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectrometry. The most intense absorption of Y 2 MoO 6 host occurred at 367 nm. Energy transfer from host lattice to Sm 3+ ions could be observed, and the schematic diagram of energy transfer was constructed. The critical energy transfer distance and energy transfer mechanism between Sm 3+ ions were discussed in detail. Considering the high color purity and appropriate emission intensity, Sm 3+ doped Y 2 MoO 6 could be a promising phosphor under near ultraviolet light excitation.

Upconversion luminescence enhancement and temperature sensing behavior of F− co-doped Ba3Lu4O9:Er3+/Yb3+ phosphors

A series of Ba3Lu4O9:Er3+/Yb3+ (EYBLO) phosphors co-doped with F− ions were synthesized by a simple solid-state reaction method. The results showed that the primary rhombohedral structure was maintained and the crystal lattice began to shrink when F− ions were introduced into the host matrix to occupy the O2− site. The agglomerations and the impurities (OH− and CO2) with higher phonon energy on the sample surface could be minimized and the sample crystallinity could be improved. Under 980 nm laser diode excitation, the green and red UC emissions of the EYBLO:0.4F− sample show nearly 5- and 7.5-fold enhancements in contrast to F−-free EYBLO. The upconversion luminescence can be finely tuned from yellow to red light to some extent by increasing F− concentration. Based on pump-power dependence and decay lifetime analysis, the energy level diagram was illustrated and the upconversion energy-transfer mechanism was discussed. The green and red emission enhancements are attributed to the modification of the local crystal field of Er3+ ions and reduction of crystal site symmetry. The cross-relaxation and back-energy-transfer processes play an important role to enhance the red/green UC emission intensity ratios. The fluorescence intensity ratio technique was employed to investigate the temperature sensing behavior of the synthesized phosphors. The temperature sensing properties can be enhanced by doping of F− ions, and the maximum sensitivity is found to be 44.57 × 10−4 K−1 at 523 K. It is promising to provide an alternative approach for enhancing UC luminescence and the temperature sensitivity in oxide matrixes and then obtain high-quality optical temperature-sensing materials by simply co-doping F− ions.

Experimental study and thermodynamic calculation of Lu2O3-SiO2 binary system

Abstract As a binary system of BaO-Lu 2 O 3 -SiO 2 ternary system, Lu 2 O 3 -SiO 2 system was optimized and calculated by CALPHAD approach based on available phase diagram and relevant thermodynamic data of RE 2 O 3 -SiO 2 (RE=Lu, Yb, Y) binary systems as well as our experimental data of Lu 2 O 3 -SiO 2 system obtained by quenching experiment. The Gibbs free energy of high temperature solution was described by an ionic two-sublattice model as (Lu 3+ ) P (O 2– , SiO 2 0 ) Q . The calculated phase diagram below 1873 K was in good agreement with experimental data at 1573, 1773 and 1873 K. The calculated Gibbs energies of two intermediate phases Lu 2 SiO 5 and Lu 2 Si 2 O 7 , the activity of Lu 2 O 3 and SiO 2 and specific heat capacities of intermediate phases agreed well with experimental results of Y 2 O 3 -SiO 2 system. This tentative study will offer help for the research of single-phase phosphor and related metallurgical slags, refractories, high-temperature superconductivity material systems.