Crystal structure, vibrational spectroscopy, and microwave dielectric properties of CaAl4O7 ceramics with low permittivity
Crystal structure, vibrational spectroscopy, and microwave dielectric properties of CaAl4O7 ceramics with low permittivity
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低介电常数CaAl4O7陶瓷的晶体结构、振动光谱和微波介电性能
DOI：
10.1007/s10854-020-03001-w
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发表时间：
2020-02
期刊：
影响因子：
--
通讯作者：
Song Kai Xin
中科院分区：
文献类型：
--
作者：
Wu Yi（学）;Hu Cheng Chao;Liu Bing;Huang Yu Hui;Song Kai Xin
采用固相反应法制备了低介电常数CaAl4O7陶瓷，首次揭示了其微波介电性能。X射线衍射谱和Rietveld精修结果表明，CaAl4O7陶瓷为单斜晶系，空间群为C2/c，晶胞参数为a = 12.89382？，b = 8.8905？，c = 5.44898？和β = 106.84771°。由于致密化程度的提高，εr随烧结温度的升高而单调增加，而τf值的变化不明显。QF值提高到最大值25,500 GHz，然后略有恶化。Qf值的变化趋势可以从外在参数上得到解释。此外，从红外反射光谱得到的内禀声子参数为进一步提高QF值提供了可能的途径。在1575℃(εr = 8.45，QF = 25,500 GHz，τf=− 98ppm/°C)下烧成的CaAl4O7陶瓷具有最佳的微波介电性能。
CaAl4O7 ceramics with low permittivity are prepared via a standard solid-state reaction method and their microwave dielectric properties are revealed for the first time. X-ray diffraction (XRD) patterns and Rietveld refinement results indicate that CaAl4O7 ceramics crystallized in monoclinic crystal symmetry with space group of C2/c. The lattice parameters are calculated as a = 12.89382 Å, b = 8.8905 Å, c = 5.44898 Å , and β = 106.84771°. εr increased monotonously with increasing sintering temperature owing to the enhancement of densification, while the variation of τf value was indistinctive. Qf value was improved to the maximum value of 25,500 GHz and then deteriorated slightly. The variation trend of Qf value could be explained from the extrinsic parameters. Moreover, the intrinsic phonon parameters obtained from the infrared reflectivity spectra provided possible routes for further improvement of Qf values. The optimal microwave dielectric properties of CaAl4O7 ceramics were obtained when sintered at 1575 °C (εr = 8.45, Qf = 25,500 GHz, τf = − 98 ppm/°C).
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