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

In this study, MgxY3-xAl5-xSixO12 (x = 0-0.6) ceramics were prepared via a high-temperature solid state method. Mg2+ and Si4+ replacing Y3+ ions at A-site and Al3+ at C-site in garnet-type Y3Al5O12 (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 Mg2+-Si4+, 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 MgAl2O4 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 MgxY3-xAl5-xSixO12 ceramics. Specially, Mg0.1Y2.9Al4.9Si0.1O12 showed a good set of microwave dielectric properties sintered at 1575 degrees C for 4 h with epsilon(r) = 10.67, Q x f = 58,799 GHz, tau(f) = -29.5 ppm/degrees C.