Pengde Han

Synthesis and photoluminescence of Eu3+-activated double perovskite NaGdMg(W, Mo)O6 – a potential red phosphor for solid state lighting

A novel high-efficiency double perovskite NaGdMg(W, Mo)O6:Eu phosphor is obtained by an improved citrate–EDTA complexing method. An emission intensity over twenty times that of a commercial red phosphor is observed. The host material has high-efficiency absorption, high doping concentration for many rare earth ions and intense emission with different colors.

Citrate sol-gel combustion preparation and photoluminescence properties of YAG:Ce phosphors

Abstract Yellow-emitting YAG:Ce 3+ nanocrystalline phosphors were prepared by citrate sol-gel combustion method using citric acid as the fuel and chelating agent. The influence of mole ratio of citric acid to metallic ions (MRCM), pH value of the solution, calcination temperature and Ce-doped concentration on the structures and properties of as-prepared powders were investigated in detail. Higher crystallinity and better luminescence performance powders were obtained at MRCM=2, pH=3 and the calcination temperature of 1200 °C. The phosphors exhibited the characteristic broadband visible luminescence of YAG:Ce. The optimum concentration of Ce 3+ was 1.0 mol.%, and the concentration quenching was derived from the reciprocity between electric dipole and electric quadrupole (d-q). Especially, the pH value of the solution was a key factor to obtain a stable sol-gel system and then obtain pure and homogeneous rare earth ions doped YAG phosphors at a lower temperature. The Y 3 Al 5 O 12 :Ce 0.03 phosphor with optimized synthesis-condition and composition had a similar luminescence intensity with the commercial phosphor YAG:Ce.

Effects of rare earth oxides on dielectric properties of Y2Ti2O7 series ceramics

Abstract A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method. The effects of rare earth oxide (La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Dy2O3) and Nd2O3 doping content on the microstructure and dielectric properties of Y2Ti2O7 ceramics were investigated. The experimental results showed that the rare earth ions were considered to dissolve in Y-sites of the pyrochlore structure, different rare earth oxides and concentration had different influences on Y2Ti2O7 ceramics. It was found that the rare earth oxide could decrease dielectric loss obviously, and the tf could be adjusted to zero with proper concentration. The Y2Ti2O7 ceramics with 1 mol.% neodymium oxide(Nd2O3) added showed optimum comprehensive properties, with the sintering temperature 1450 °C, the permittivity 45, the value of Q·f 22000 GHz, and the tf value 179 ppm/°C, while 1 mol.% Nd oxide (Nd2O3) was added.

Effective red compensation of Sr 2 SiO 4 : Dy 3+ phosphor by codoping Mn 2+ ions and its energy transfer

Mn2+ ions codoped Sr2SiO4 : Dy3+ phosphors were prepared by the solid-state reaction method using NH4Cl as the flux. Their phase compositions, photoluminescence properties, and the energy transfer process were systematically investigated. All Mn/Dy codoped powders were α′-Sr2SiO4. The codoping concentration range of Mn2+ was ≤ 4.0mol% to keep the structure undamaged. The broad red emission of Mn2+ centered at 647nm in Sr2SiO4 :Mn, Dy powders, which effectively compensated the red emission of Sr2SiO4 : Dy3+ phosphor. The CIE chromaticity coordinates dramatically changed from (0.310, 0.340) to (0.332, 0.326) due to the red enhancement via the energy transfer from Dy3+ to Mn2+. This energy transfer is realized by the exchange interaction. But the luminescence quenching of Sr2SiO4 :Dy, Mn phosphor was mainly caused by the electric multipoles interaction. The concentration optimized (Sr0.96, Mn0.02, Dy0.02)2SiO4 phosphor with high and almost pure white emission has great potential to act as a single-matrix white phosphor for white LEDs.

Synthesis and co-luminescence properties of Tb3+-methacrylic acid-1,10-phenanthroline complexes doped with Eu3+

A series of rare earth complexes Tb1−xEux(MAA)3phen (x=0.00, 0.01, 0.03, 0.05, 0.07, 0.09, 0.10, 0.30, and 0.50) were synthesized with MAA as the first ligand and phen as the second ligand. The complexes were characterized by means of FT-IR, thermogravimetry-differential scanning calorimetry (TG-DSC), XRD, UV absorption spectra, and photoluminescence spectra (PL). The results show that the luminescence intensity of Eu3+ increases as Tb3+ transfer the absorbed energy to Eu3+ in the complexes. The emission of Tb3+ at 545 nm is observed and increasing with x decreasing. When x=0.01, the luminescence intensity reaches the maximum value, and the emission intensity of Tb3+ at 545 nm and Eu3+ at 614 nm are almost equal. It realizes the co-luminescence of Eu3+ and Tb3+. We can obtain complexes with different colors by adjusting the ratio of Eu3+ to Tb3+.

Optical property of SmAlO3 applied as 1.06 μm laser absorbing material

Abstract SmAlO 3 powders were successfully synthesized through the citrate sol-gel combustion method. The phase evolution of the prepared powders were characterized using thermal gravimetric (TG) analysis, differential scanning calorimetry (DSC) analysis and Fourier transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) was applied to examine the purity of the powders. The reflective properties of SmAlO 3 with changing temperatures were investigated by ultraviolet-visible near-infrared spectrophotometer (UVPC) specular reflection spectrum. The results displayed that pure SmAlO 3 phase with preferable reflectivity at 1.06 μm could be obtained at 900 °C for 2 h. Furthermore, the reflectivity of SmAlO 3 at various temperatures from −40 to 500 °C transformed within ±0.1%, and all maintained below 1% at 1.06 μm. The absorbance of SmAlO 3 in the resin solution was 2.134 and the moral absorption coefficient was about 384.8 in the work. The study indicated that SmAlO 3 powders may be a promising kind of heat resistant absorbing material for 1.06 μm laser defense, which could be further applied to laser absorbing coatings with a wide range of temperatures.

Investigation on the amounts of Na2CO3 and sulphur to obtain pure Y2O2S and up-conversion luminescence of Y2O2S:Er

The process to prepare pure phase of hexagonal Y2O2S was investigated. Effect of mixed flux of Na2CO3 and S amounts was studied. The phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the single phase of Y2O2S with smooth morphology could not be obtained as the molar ratio of Y2O3, Na2CO3 and S was in the range of 1:(0.5–1):(2–3) until the molar ratio was increased to 1:1.5:4. Different Er3+ concentration doped Y2O2S:Er powders were prepared with molar ratio of the raw materials 1:1.5:4. The quenching concentration of Er3+ in Y2O2S was more than 2 mol.%, which was due to the interaction of electric quadrupoles between Er3+ ions.