Influence of TiB₂ content and powder size on the dielectric property of TiB₂/Al₂O₃ composites

TiB₂/Al₂O₃ composites were prepared by hot-pressed sintering using TiB₂ and Al₂O₃ powders. The dielectric property of these composites was investigated. The mechanisms of polarization and microwave energy loss were discussed. Both the real part of dielectric constant and the energy loss increase greatly with increasing TiB₂ content over the frequency range 8.2-12.4 GHz. Movement and accumulation of valence electrons in TiB₂ powders caused the polarization and energy loss. The formation of a TiB₂ local network is responsible for the marked increase in the dielectric constant.