Effect of Aluminum Doping on Microwave Absorption Properties of ZnO / ZrSiO 4 Composite Ceramics

In this study, Al ‐doped ZnO particles are infiltrated into porous ZrSiO 4 substrates to form an Al ‐doped ZnO / ZrSiO 4 composite ceramic using sol‐gel process. The doping of aluminum results in the high‐concentration carriers, leading to the improvement of polarization capability and electric conductivity. When the Al content increases to 2.5 at.%, particle shape is changed from spherical into flower‐like one, and the electric conductivity of ZnO / ZrSiO 4 composite ceramics is further improved. Therefore, both dielectric loss and microwave absorption properties of ZnO / ZrSiO 4 composite ceramics increase with the increase of Al content. The further increase of Al content leads to the production of ZnAl 2 O 4 , which is a low‐permittivity ceramic, so the dielectric constant and dielectric loss of ZnO / ZrSiO 4 composite ceramics show a decreasing tendency. Owing to the higher dielectric loss, the 2.5 at.% Al ‐doped ZnO / ZrSiO 4 composite ceramics exhibit the best microwave absorption properties over the frequencies ranging from 8.2 to 12.4 GHz ( X ‐band).