Enhanced Dielectric Properties and High-Temperature Microwave Absorption Performance of Zn-Doped Al₂O₃ Ceramic

To improve the dielectric and microwave absorption properties of Al₂O₃ ceramic, Zn-doped Al₂O₃ ceramic was prepared by conventional ceramic processing. X-ray diffraction analysis confirmed that Zn atoms successfully entered the Al₂O₃ ceramic lattice and occupied Al sites. The complex permittivity increased with increasing Zn concentration, which is mainly attributed to the increase in charged vacancy defects and densification of the Al₂O₃ ceramic. In addition, the temperature-dependent complex permittivity of 3% Zn-doped Al₂O₃ ceramic was determined in the temperature range from 298 K to 873 K. Both the real and imaginary parts of the complex permittivity increased monotonically with increasing temperature, which can be ascribed to the shortened relaxation time and increasing electrical conductivity. The increased complex permittivity leads to a great improvement in microwave absorption. In particular, when the temperature is up to 873 K, the 3% Zn-doped Al₂O₃ ceramic exhibited the best absorption performance with a maximum peak (−12.1 dB) and broad effective absorption bandwidth (reflection loss less than −10 dB from 9.3 GHz to 12.3 GHz). These results reveal that Zn-doped Al₂O₃ ceramic is a promising candidate for use as a kind of high-temperature microwave absorption material.