Hong Guangyan

Preparation and Characterization of W-Type Hexaferrite Doped with La3+

Abstract A series of W-type ferrites with the composition of Ba 1-x ,La x Co 2 Fe 16 O 27 (where, x =0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) were prepared by solid-state reaction method. The structure transformations of the ferrites were examined by XRD, DTA-TG and XPS, and the microwave-absorbing properties were investigated by evaluating the permeability and permittivity of materials ( μ x ɛ r ). The results showed that the phase-transition temperature increased with the addition of La 3+ content, and a single-phase was formed at 1250 °C at last. Microwave properties were obviously improved as a result of the substitution of La 3+ for Ba 2+ at the frequency range of 0.5 ∼ 18.0 GHz.

Relationship between Crystal Structure and Luminescence Properties of (Y0.96 - x Lnx Ce0.04)3 Al5 O12 (Ln = Gd, La, Lu) Phosphors

Abstract The doping effects of La3+, Gd3+ and Lu3+ on the crystal structure and luminescence properties of (Y0.96 - x Lnx Ce0.04)3 Al5 O12 (Ln = Gd, La, Lu) Phosphors were studied. The X-ray diffraction patterns presented that with the increase of the doping concentrations of La3+ and Gd3+ ions, the d-value of (Y0.96 - x Lnx Ce0.04)3 Al5 O12 (Ln = Gd, La, Lu) increased and the larger the doping ion, the stronger the effect would be. The doping amount causing phase transition in (Y0.96 - x Lnx Ce0.04)3 Al5O12 decreased with the increase of the ionic radii of the doping lanthanide ions (La3+ : 0.106 nm, Gd3+ : 0.094 nm, Lu3+ : 0.083 nm). The bigger doping ion of Gd3+ made the emission of (Y0.96 - x Gdx Ce0.04)3 Al5O12 move to red spectral region, but the smaller one of Lu3+ made it blue.

Synthesis and Characterization of Terbium-Trimesic Acid Luminescent Complex in Polyvinylpyrrolidone Matrix

Tb(III)-trimesic acid (TMA) luminescent complexes were synthesized in the polyvinylpyrrolidone (PVP) matrix. The elemental analysis, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and fourier-transform infrared spectroscopy (FT-IR) indicated that its chemical constitution is PVP/Tb(MTA)·4H2O. The XRD patterns showed that the complex is a new kind of crystal. The TEM image indicates that the complex is rod shaped. The rod diameter is about 200 nm, and the length ranges from hundred of nanometer to a few micrometers. In addition, the dispersity is better. TG-DTA curves indicate that the complex is thermally stable before 463 °C. Photoluminescence analysis indicates that the complex emits Tb3+ characteristic luminescence under ultraviolet excitation.

Luminescent Properties of Gd3PO7:Eu in UV/VUV Region

The luminescent properties of Gd3PO7:Eu were investigated in W and VUV regions. This phosphor has such strong emissions around 618.5 nn under UV excitation, especially around 209nn, that it has a better colour saturation than that of Y2O3:Eu. It could be a new potential red phosphor for lamp and other applications with W-excitation source or even for displaying devices. In the VUV excitation spectrum of Eu3+ emissions, energy absorptions by Gd3+, Gd-O and PO43- have been observed, on which it can be inferred that there are three kinds of energy transferring processes to Eu-3(+) ions. The energy absorptions of Gd3+, Gd-O and PO43- are induced by 4f --> 4f transitions, a bandgap transition of Gd3PO7 and intramolecular (2t(2) --> 2a, 3t(2)) transition, respectively. The energy transfer efficiency of the PO43- intramolecular transition is lower compared with that of the bandgap transition (Gd-O).

Preparation of nanocrystalline ZrO2 by reverse precipitation method

Nanocrystalline ZrO2 particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD patterns show that the synthesized ZrO2 is monoclinic in structure with space group P21/a when calcination temperature is in the range of 400–1000°C. It is found that the smaller the particle, the bigger the crystal lattice distortion, the worse the crystal growth, and the lower the diffraction intensity. TEM images reveal that ZrO2 particles are spherical in shape, and the particle size distribution is in, narrow range. The mean sizes of the particles increase with the increase of calcination temperatures. It is first to observe the streaks of different crystallographic planes. Thermogravimetric analysis indicates that the crystallization temperature of ZrO2 is 461.32°C. Measurement of ZrO2 relative density shows that the relative density of nanocrystalline ZrO2 powders increases with the increasing of ZrO2 particle sizes.