Sintering behavior, phase composition, microstructure, and dielectric characteristics of garnet-type Ca3Fe2Ge3O12 microwave ceramics

Abstract

This paper describes the solid-state production of a unique yellowish-grey microwave dielectric ceramic, Ca3Fe2Ge3O12 (CFG). Rietveld refinement demonstrated that CFG corresponds to a cubic system (space group 230: Ia 3¯ d). The relative density of the ceramic initially increased and then decreased with the sintering temperature, reaching a maximum of 96.92% at 1 330 °C. According to scanning electron microscopy and energy-dispersive spectroscopy results, the CFG ceramic grains are spherical and consistent in size; furthermore, they have distinct grain boundaries and a uniform distribution of the four constituent elements. The CFG ceramic has a superior crystal structure and a high crystallinity, according to transmission electron microscopy. Raman spectroscopy revealed that the Q×f value of the ceramic and the full width at half maximum of the Raman peak are negatively correlated. The ceramic possesses the best overall dielectric characteristics after sintering at 1 330 °C for 4 h: εr = 10.31, Q×f = 82 636 GHz, and τf = −45.66 × 10−6 °C−1, showing that it is a promising candidate for use in mobile devices.

Keywords

• Low permittivity
• Garnet-type structure
• Microwave dielectric properties
• Ca3Fe2Ge3O12