Effect of raw materials type on the sintering ability and microwave dielectric properties of Mg_2.15Al₄Si₅O₁₈ ceramics

In this work, Mg_2.15Al₄Si₅O₁₈ ceramics were synthesized by solid-state sintering method using silicon oxide and silicic acid as silicon raw materials respectively. And their crystal structure, surface topography, microwave dielectric properties were characterized. X-ray diffraction shows that the main crystal phase can be formed by using silicon oxide or silicic acid as raw material. Low permittivity (ε_r) of 4.26 (MAS–SiO₂) and 4.34 (MAS–H₂SiO₃), quality factor (Q × f) of 29,669 GHz (MAS–SiO₂) and 68,856 GHz (MAS–H₂SiO₃), and temperature coefficient of resonant (τ_f) of − 27.87 ppm/°C (MAS–SiO₂) and − 25.89 ppm/°C. MAS–H₂SiO₃ ceramic has better density and higher Q value than MAS–SiO₂ ceramic.