Crystal structure and microwave dielectric properties of Mg2+-Si4+ co-modified yttrium aluminum garnet ceramics

In this article, garnet-type Y 3 Al 5 O 12 (YAG) were doped with Mg 2+ -Si 4+ ionic pairs and its effect on the structure and the microwave dielectric properties was investigated. It was revealed that in ceramics Y 3 Mg x Al 5-2 x Si x O 12 ( x  = 0, 0.5, 1.0, 1.5, 2.0), increasing doping concentration decreased the sintering temperature and time for the optimal densification. X-ray diffraction studies showed that the samples are isostructural to Al 5 Y 3 O 12 garnet. All sample were formed a single phase except for x  = 2.0, where a secondary peak was detected. Excellent microwave dielectric properties of ε r  = 10.56, Q  ×  f  = 67,571 GHz and τ f  = -35.23 ppm/°C were obtained for Y 3 Mg 0.5 Al 4 Si 0.5 O 12 ceramics sintered at 1625 °C for 5 h. The factors influencing the microwave dielectric properties of Y 3 Mg x Al 5-2 x Si x O 12 ceramics were further discussed by considering the ionic polarization, packing fraction, average grain size and chemical bond valence theory.