Enhanced mechanical, dielectric, and microwave absorption properties of ZnO/ZrSiO4 composite ceramics by adding Al2O3 powders

The ZnO/ZrSiO4 composite ceramics with different Al2O3 additions are fabricated by pressureless sintering method. The addition of Al2O3 contributes to the formation of ZnAl2O4, which results in the enhancement of bulk densities as well as flexural strengths of the ceramics by promoting the mass transportation movement. Both the complex permittivity and dielectric loss increase firstly then decrease as the Al2O3 content enhances from 0 to 7 wt%. The bulk density and ZnO content are the main factors to affect the dielectric performance of the ceramics. Owing to the higher dielectric loss, the ceramic with 3 wt% Al2O3 addition presents the better microwave absorption property. The effective absorption bandwidth of the ceramic in 2.4 mm thickness is 8.8-11.9 GHz, with a minimum reflection loss of -25.36 dB at 10.4 GHz. As the thickness of the ceramic increases, the absorption peak shifts toward the lower frequency region, which indicates the absorption bandwidth can be tailored by changing the thickness. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)