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

Gehlenite‐typed Ca2Al2SiO7 ceramics were prepared by the conventional solid‐state reaction. Two anomalies were found in the plot of dielectric constant vs. temperature, which was associated to space charge polarization. Pure phase crystal structure and no phase transition were observed in the temperature dependent XRD patterns and Raman spectra from room temperature to 900°C. There was relevant relation between Q× f and τƒ with the stretching vibrations of Ca‐O bond and O‐Ca‐O bending in CaO8 polyhedron. Excellent microwave dielectric properties (εr = 8.86, Q × f = 22,457GHz, and τf = −51.06 ppm/°C) were obtained for Ca2Al2SiO7 sintered at 1440°C in air, which had the potential application to use in microwave and millimeter‐wave devices such as capacitors and substrates.