Crystal structure and microwave dielectric properties of CaCuGe2O6 pyroxene-type ceramics

Abstract

Microwave dielectric ceramics with low permittivity (ε_r < 15) have become a critical research focus in the millimeter-wave communication era due to their ultra-low dielectric loss and high-frequency stability, especially as the rapid global proliferation of 5G and 6G communication technologies continues. In this study, the phase evolution of CaCuGe₂O₆ ceramics was systematically investigated using X-ray diffraction (XRD) combined with Rietveld refinement. The results revealed that, with increasing sintering temperature, secondary phases in the material gradually decomposed, ultimately enabling the successful preparation of single-phase CaCuGe₂O₆ ceramics (space group: P2₁/c) under optimal sintering conditions. Scanning electron microscopy (SEM) characterization showed that samples sintered at 1020 °C exhibited optimal surface morphology, achieving superior microwave dielectric properties (ε_r = 8.86, Q × f = 21 301 GHz, τ_f = −90.26 ppm °C⁻¹) and high densification. A thorough investigation of the factors governing performance established correlations between density and both ε_r and Q × f values, as well as the evolution of temperature stability with sintering temperature. It has been demonstrated that CaCuGe₂O₆ ceramics have significant potential as novel materials for core components such as base-station filters and antenna substrates, offering new insights into the design of high-frequency communication devices.