Temperature‐dependent dielectric and Raman spectra and microwave dielectric properties of gehlenite‐type Ca₂Al₂SiO₇ ceramics

Abstract

Gehlenite-type Ca 2 Al 2 SiO 7 ceramics were prepared by the conventional solid-state reaction. Two anomalies were found in the plot of dielectric constant vs temperature, which were associated with space charge polarization. Pure phase crystal structure and no phase transition were observed in the temperature-dependent X-ray diffraction (XRD) patterns and Raman spectra from room temperature (RT) to 900°C. There was relevant relation between Q × f and τ ƒ with the stretching vibrations of Ca-O bond and O-Ca-O bending in CaO 8 polyhedron. Excellent microwave dielectric properties (ε r = 8.86, Q × f = 22 457 GHz, and τ f = −51.06 ppm/°C) were obtained for Ca 2 Al 2 SiO 7 sintered at 1440°C in air, which had the potential application to use in microwave and millimeter-wave devices such as capacitors and substrates. K E Y W O R D S 5G, microwave ceramics, silicate dielectrics 772 | SONG et al.

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Crystal Structure and Ferroelectric Evidence of BaZnSi3O8, a Low‐Permittivity Microwave Dielectric Ceramic

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New low‐εr, temperature stable Mg3B2O6‐Ba3(VO4)2 microwave composite ceramic for 5G application

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