Ionic occupation, structures, and microwave dielectric properties of Y 3 MgAl 3 SiO 12 garnet‐type ceramics

The Y 3 MgAl 3 SiO 12 ceramics with pure phase were successfully synthesized by solid‐state sintering reaction method for the first time. Their microwave dielectric properties were investigated as a function of sintering temperature. Their microstructure characteristics and ionic occupation sites of tetrahedral and octahedral units were characterized and analyzed by SEM & energy dispersive spectrometer ( EDS ) and Rietveld refinement of X‐ray powder diffraction data. Crystal structure of Y 3 MgAl 3 SiO 12 is isostructural to Y 3 Al 5 O 12 with a cubic garnet structure and space group of I a ‐3 d , which contains YO 8 dodecahedra, (Mg/Al oct )O 6 octahedral, and (Si/Al tet )O 4 tetrahedral units. The Q f and ε r values of different samples are strongly dependent on the distribution of grain sizes, grain sizes, and porosity. The samples sintered at 1550°C exhibit optimized microwave dielectric properties with relative permittivity (ɛ r ) of 10.1, Q f values of 57 340 GH z (at 9.5 GH z), and τ f values of −32 ppm/°C. Such properties indicate potential application of Y 3 MgAl 3 SiO 12 as microwave substrates.