Lattice occupying sites and microwave dielectric properties of Mg2+–Si4+ co-doped MgxY3-xAl5-xSixO12 garnet typed ceramics

In this study, Mg x Y 3- x Al 5- x Si x O 12 ( x  = 0–0.6) ceramics were prepared via a high-temperature solid state method. Mg 2+ and Si 4+ replacing Y 3+ ions at A-site and Al 3+ at C-site in garnet-type Y 3 Al 5 O 12 (YAG) ceramics were designed to discuss the effects of crystal structure, microstructure on microwave dielectric properties for the first time. Liquid phase sintering induced by doping of Mg 2+ -Si 4+ , significantly decreased the sintering temperature and time for the densification of YAG ceramics. X-ray diffraction of the samples showed single phase for x  ≤ 0.5, while a secondary phase of MgAl 2 O 4 formed for x  = 0.6. From the Rietveld analysis, a decrease in lattice dimensions, bond length and valence and rattling effect were observed, while Raman results showed a change in FWHM of the Eg mode. Based on these parameters, a structure–property relation was developed for Mg x Y 3- x Al 5- x Si x O 12 ceramics. Specially, Mg 0.1 Y 2.9 Al 4.9 Si 0.1 O 12 showed a good set of microwave dielectric properties sintered at 1575 °C for 4 h with ε r  = 10.67, Q  ×  f  = 58,799 GHz, τ f  = -29.5 ppm/°C.