We investigated the phase evolution, microstructure, and microwave dielectric properties of Na- and Zr-doped Ba(Mg0.5W0.5)O3 [i.e., (Ba1-2xNa2x)(Mg0.5-xZrxW0.5)O3] ceramics. BaWO4 as a secondary phase was observed in all compositions, and it increased as the dopant concentration increased. All specimens revealed a dense microstructure. For the composition of x=0.01, polyhedral grains were observed. As the dopant concentration increased, the densification and the grain growth were promoted by a liquid phase. The quality factor(Q×f0) decreased remarkably, whereas the dielectric constant (εr) tended to decrease as the dopant concentration increased. The dielectric constant, quality factor, and temperature coefficient of the resonant frequency of the composition of x=0.01 sintered at 1,700℃ for 1 h were 18.6, 216,275 GHz, and -22.0 ppm/℃, respectively.
We investigated the physical properties of stoichiometric and non-stoichiometric oxide doped complex perovskite, Ba(Zn1/3Ta2/3)O3 ceramics and their impacts on the microwave dielectric performances using various characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and network analyzer. According to the measurement of lattice constant changes, anomalous lattice volume contraction of ZrO2 doped Ba(Zn1/3Ta2/3)O3 sample only showed the dielectric quality factor enhancements, which was due to the lattice volume contraction as well as the 1:2 B-site cation ordering. In addition, NiO doping was useful to the stabilization of temperature coefficient of resonance frequency.
A Study on the Enhancement of Cooling Efficiency for the Cabinet of Automatic Controller in the Interior of Industrial Building Soon-Ho Kim, Hyun-Jung Park Journal of the Korea Society For Power System Engineering.2013; 17(6): 79. CrossRef
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