Microwave dielectric properties and microstructures of xBa0.33Sr0.67TiO3–(1−x)Ba4Sm9.33Ti18O54 ceramics with near-zero temperature coefficient
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The phase composition, microstructures, sintering behavior, and microwave dielectric properties of Ba0.33Sr0.67TiO3–Ba4Sm9.33Ti18O54 ceramics prepared via conventional solid-state route were systematically investigated as a function of the Ba0.33Sr0.67TiO3 molar fraction and sintering temperature. All the sintered ceramics only exhibited a single orthorhombic tungsten bronze structure BaSm2Ti4O12 phase. And all samples sintered at 1400 °C showed fully dense and homogeneous microstructures. The variation of bulk density and dielectric properties are related with the Ba(Zn1/3Nb2/3)O3 molar fraction, but not with a same trend. As Ba ions in A1 sites are substituted by Sr ions, Q × f values enhanced dramatically. The optimum microwave dielectric properties with an εr value of 80.13, a Q × f value of 11386 GHz (at 3.5 GHz), and a τf value of − 0.34 ppm/°C were obtained for 0.03Ba0.33Sr0.67TiO3–0.97Ba4Sm9.33Ti18O54 ceramics sintered at 1400 °C for 4 h.
The authors are grateful to the support of Program for Advanced Research and Key Technology in Industry of Jiangsu Province (Grant No. BE2015007-1), the Talent Introduction Project of Jiangsu University of Technology (Grant No. KYY16030), the National Natural Science Foundation (Grant No. 51475219), the National Science and Technology Major Project (Grant No. 2018ZX04026001-008), and Major project of natural science research in universities of Jiangsu: Research on key technology of material/structure integrated design of CFRP car body (Grant No. 16KJA460002).
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