ABSTRACT
MgNb2O6 ceramics doped with (Li2O-MgO-ZnO-B2O3-SiO2) glass were synthesized by the traditional solid phase reaction route. The effects of LMZBS addition on microwave dielectric properties, grain growth, phase composition and morphology of MgNb2O6 ceramics were studied. The SEM results show dense and homogeneous microstructure with grain size of 1.72 µm. Raman spectra and XRD patterns indicate the pure phase MgNb2O6 ceramic. The experimental results show that LMZBS glass can markedly decrease the sintering temperature from 1300 °C to 925 °C. Higher density and lower porosity make ceramics have better dielectric properties. The MgNb2O6 ceramic doped with 1 wt% LMZBS glass sintered at 925 °C for 5 h, possessed excellent dielectric properties: ε r = 19.7, Q·f = 67 839 GHz, τ f = -41.01 ppm °C-1. Moreover, the favorable chemical compatibility of the MgNb2O6 ceramic with silver electrodes makes it as promising material for low temperature co-fired ceramic (LTCC) applications.
ABSTRACT
Low loss Li2NiZrO4 ceramics with rock salt structure were successfully prepared by the solid-phase reaction method. The relationship between sintering temperature, phase composition and dielectric properties of Li2NiZrO4 ceramics was reported for the first time. The grain size gradually increased and the porosity decreased with the sintering temperature increasing. When the sintering temperature exceeds 1300 °C, the grains grow abnormally and some grains begin to melt. The XRD patterns indicated the second phase ZrO2 appeared due to the volatilization of lithium. The grains grow abnormally and a second phase of ZrO2 increased the loss of Li2NiZrO4 ceramics. The samples sintered at 1300 °C possessed the best dielectric properties: ε r = 12.3, Q f = 20000 GHz, τ f = -23.4 ppm °C-1, which would make the ceramic a possible candidate for millimeter-wave applications.
ABSTRACT
An electron beam inducing method for sprouting large quantities of silver nanoparticles on the surface of silver chloride particles is reported. The electron beam driven process was characterized by time-dependent scanning electron microscope (SEM) and energy dispersive spectrum (EDS), allowing for observing several key intermediates in and characteristics of the growth process. Theoretical calculation coupled with experimental observation demonstrated that the growth of silver nanoparticles was mostly related to the current density of electron beam. Decomposition of the silver chloride on the surface of sample was under electron beam irradiation resulted in silver nanoparticles and chlorine. This phenomenon could be useful in developing a novel mechanism for preparation of nanostructures and proposing a reference to avoid image distortion during the characterization of silver compounds under SEM.
ABSTRACT
The matrix effect, spectral overlap and background were investigated for X-ray fluorescence (XRF) spectrometric determination of rhenium content according to the analysis requirement of rhenium-tungsten alloys, a key material used in traveling wave tube. The reason for causing the calibration curve nonlinear was explained theoretically when binary ratio technique of XRF was used. Both theoretical and experimental results show that linear calibration curve can be obtained if the curve is plotted by Re% vs. Re Lalpha X-ray intensity instead of binary ratio technique. The method is rapid and accurate and the results obtained in this work are in good agreement with those of chemical analysis. The method has been successfully applied to product quality control.
