Effect of Mg doping on microwave dielectric properties of translucent polycrystalline alumina ceramic

In this paper, the microstructure and microwave dielectric properties of translucent polycrystalline alumina (PCA) with various addition amounts of MgO were investigated. Translucent PCA was obtained by adding ∼500–2000 ppm MgO. Compared with the undoped PCA, the translucent PCA doped with 500 ppm MgO showed a higher density and a much higher Q×f value. As the MgO content further increased, the dielectric constants (εr) of the translucent PCA samples showed no significant change, while the Q×f values decreased rapidly. The increased amount of impurities (MgO or spinel) was believed to be the main reason for the lower Q×f values.