Microwave dielectric properties of YAG ceramics prepared by sintering pyrolysised nano-sized powders

YAG ceramics with good dielectric properties were prepared via a modified pyrolysis method, with yttrium nitrate as the yttrium source and combined aluminium sulphate and aluminium nitrate as aluminium sources, and subsequent sintering in a muffle furnace. The effects of the different aluminium sources on the powder characteristic and the impact of sintering temperature, sintering aids (TEOS) and additive (TiO2) on the dielectric properties of the ceramics were studied. The results show that well-dispersed pure YAG nano-powders can be obtained after calcination at 1000 °C with an aluminium sulphate and aluminium nitrate molar ratio of 1.5:2. The relative density, permittivity (εr) and quality factor (Q×f) of the YAG ceramics increase with sintering temperature and TEOS addition. TiO2 can greatly promote τf to near-zero but decreases Q×f. The relative density, εr, Q×f and τf of the YAG–1 wt% TEOS–1 wt% TiO2 ceramic obtained at 1520 °C are 97.6%, 9.9, 71, 738 GHz and −30 ppm/°C, respectively.