Preparation and properties of nanocrystal SmBO_3 by nitrate-citrate sol-gel combustion method

Nanocrystal SmBO3 powders were synthesized by nitrate-citrate sol-gel combustion method. The phase evolution, morphologies and absorbency of the synthesized powders were characterized by X-ray diffraction （XRD）, Field emission scanning electronic microscope （FESEM）, Fourier transform infrared spectroscopy （FFIR） and UV-3101PC spectrophotometer （UVPC）, respectively. XRD and FESEM results showed that pure SmBO3 phase was obtained at 750 ℃, with an average original particle size of about 100 nm. FTIR showed that there were apparently concentrated absorbent peaks between 500 and 1400 cm^-1. Moreover, the reflectivity of the powders apparently decreased at the wavelength between 1.05 and 1.15 μm. Therefore, SmBO3 might be a kind of absorbent material for infrared laser.

Fabrication and optical properties of a highly transparent Nd:YAG ceramic

A neodymium doped yttrium aluminum gamet （Nd：YAG） transparent ceramic was fabricated by a solid state reaction method using commercial α-Al2O3, Y2O3, and Nd2O3 powders as starting materials and tetraethyl orthosilicate （TEOS） as sintefing aid. The morphology and microstructure of the nanopowders and the Nd：YAG transparent ceramic were investigated. The fully dense Nd：YAG ceramic with an average grain size of-20 μm was obtained by vacuum sintering at 1720℃ for 12 h. Few pores and grain-boundary phases were observed. The in-line transmittance of the ceramic was 81.5% at 1064 nm.

Microwave electromagnetic and absorbing properties of Dy^(3+) doped MnZn ferrites

Dy3+ doped Mn-Zn ferrites Mn0.3Zn0.7Fe2-xDyxO4(x=0,0.01,0.02,0.03,0.04)were prepared by the conventional solid-state reaction.The crystal structure,surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction analysis(XRD),scanning electron microscopy(SEM) and network analyzer(Agilent 8722ET).All the XRD patterns showed the single phase of the spinel-type ferrite without other intermediate when x≤0.03.The average crystallite size was about 44?56 nm.The mi...

Preparation and properties of Nd:YAG ultra-fine powders

Ultra-fine Nd：YAG powders with different doping concentrations were synthesized by sol-gel combustion method. The pure Nd：YAG could be prepared at the low temperature of 900℃. Ethanol could improve the dispersity of powders, and the average size of the ultra-fine powders was around 250 nm. The reflection spectrum showed that there were several apparent characteristic absorption peaks and the intensity of these peaks enhanced with the increasing concentration of Nd^3＋. The luminescence spectrum, which was excited by 808 nm wavelength, exhibited several obvious emission bands in the range of 900-1150 nm. The emission intensity of Nd：YAG powders increased until the Nd content was above 3 mol.% due to the fluorescent quenching effect.

Optical property of SmAlO_3 applied as 1.06 μm laser absorbing material

SmAlO3 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 re-flective properties of SmAlO3 with changing temperatures were investigated by ultraviolet-visible near-infrared spectrophotometer （UVPC） specular reflection spectrum. The results displayed that pure SmAlO3 phase with preferable reflectivity at 1.06μm could be obtained at 900 oC for 2 h. Furthermore, the reflectivity of SmAlO3 at various temperatures from-40 to 500 oC transformed within ±0.1%, and all maintained below 1%at 1.06μm. The absorbance of SmAlO3 in the resin solution was 2.134 and the moral absorption coefficient was about 384.8 in the work. The study indicated that SmAlO3 powders may be a promising kind of heat resistant absorb-ing material for 1.06μm laser defense, which could be further applied to laser absorbing coatings with a wide range of temperatures.

Microwave Absorbing Properties of Magnesium-substituted MnZn Ferrites Prepared by Citrate-EDTA Complexing Method

Magnesium-substituted MnZn ferrites with composition of Mn0.4Zn0.6MgxFe（2-x）O4（x=0.00,0.05） were prepared by citrate-EDTA（ethylenediamine tetraacetic acid） complexing method.The crystal structure,surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction（XRD） analysis,scanning electron microscopy（SEM） and network analyzer（Agilent 8722ET）.All the XRD patterns showed the single phase of the spinel-type MnZn ferrite without other intermediate phase.The lattice parameter and average particle size increased with the substitution of magnesium.The microwave electromagnetic properties of the samples have been studied at the frequency range from 2 to 18 GHz.It was shown that the values of ε′ and ε″ decreased slightly with the substitution of magnesium.The values of μ′ and μ″ were improved significantly,and the peak of μ″ shifted to low frequency with Mg2＋ ions substituting.Furthermore,the reasons have also been discussed by using electromagnetic theory.The reflection loss（RL） ascended after magnesium was substituted.Magnesium-substituted ferrite had excellent microwave absorption properties.The frequency（with respect to-10 dB） started from 11.3 GHz,and the bandwidth reached about 3.5 GHz.The peak value of RL was about-19 dB at a matching thickness of 3.1 mm.

Effects of rare earth oxides on dielectric properties of Y_2Ti_2O_7 series ceramics

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 cerami...

Optimization on dielectric properties of Y_2Ti_2O_7 ceramics with Bi_2O_3-Nd_2O_3-Nb_2O_5 co-doping

The present work aimed to explore a kind of microwave dielectric materials with middle-permittivity, high Qf, near-zero τf, and lower sintering temperature. A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method. For improving the dielectric properties of Y2Ti2O7 system, Bi2O3, Nd2O3 and Nb2O5 were added and their effects on phase composition, micro-structure, and dielectric properties at microwave frequencies were investigated by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The queuing score method for multi-target orthogonal design was used to obtain the optimum prescription. The results showed that the Y2Ti2O7 ceramics with 8 wt.% Bi2O3 and 1 mol.% Nd2O3-Nb2O5 were well sintered at 1350 ℃, exhibiting excellent dielectric characteristics, i.e. εr≈76, Qf≈18980 GHz, τf =＋25.5 ppm/℃.

Er^(3+)-substituted W-type barium ferrite: preparation and electromagnetic properties

Er3+-substituted W-type barium ferrites Ba1-xErx(Zn0.3Co0.7)2Fe16O27 (x=0.00, 0.05, 0.10, 0.15, 0.20) were synthesized by polymer adsorbent combustion method. Samples were characterized by X-ray diffraction analysis (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and network analyzer to investigate the relationships among Er3+ concentration, crystal structure, surface morphology and electromagnetic properties. All the XRD patterns showed pure phase of W-type barium ferrite when x≤0.15, while the impurity phase of ErFeO3 appeared when x=0.20. The pure W-type barium ferrite showed a hexagonal flake shape. In addition, the microwave electromagnetic properties of samples were analyzed in the frequency range of 2-18 GHz. It was indicated that the electromagnetic properties were significantly improved when Er3+ doping content was 0.10. The reasons were also discussed using electromagnetic theory. The optimized ferrite exhibited excellent microwave absorption performance. The maximum of reflection loss (RL) reached about-27.4 dB and RL was below-10 dB at the frequency range from 8.4 GHz to 18 GHz, when the thickness was 2.6 mm.