Structure and Microwave Dielectric Properties of Hexagonal Ba[Ti1−x(Ni1/2W1/2)x]O3 Ceramics |
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Authors: | Fei Zhao Zhenxing Yue Jing Pei Hao Zhuang Zhilun Gui Longtu Li |
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Affiliation: | State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China |
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Abstract: | Microwave dielectric ceramics with the composition of BaTi1? x (Ni1/2W1/2) x ]O3 ( x =0.4–0.6) were prepared by a solid-state reaction method. The evolution of the crystalline phases was investigated by X-ray powder diffraction analysis. A cubic-to-hexagonal phase transition occurred between 1000° and 1300°C. The phase transition is irreversible; thus, the hexagonal phase remains stable at room temperature. The X-ray powder diffraction data for x =0.5 were refined using the Rietveld method. It was identified as a h -BaTiO3-type hexagonal perovksite with the space group of P 63/ mmc . It also reveals that random occupancy of Ti4+ and W6+ ions occurs in the B-site substructures, whereas Ni2+ ions exclusively occupy the octahedral site in the corner-sharing octahedron. The dielectric properties of dense-sintered ceramics were characterized at microwave frequencies. With an increase in x from 0.4 to 0.6, the Q × f value increased from 26 700 to 42 000 GHz, whereas ?r decreased from 29.8 to 20.0, and τf from +6.5 to ?9.9 ppm/°C. |
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