A Defect Perspective on High Thermal Conductivity Al2O3–TiO2 Dielectric Ceramics

The development of high-power millimeter-wave technology introduces new requirements on microwave dielectric ceramics. In addition to lower dielectric loss, higher thermal conductivity is also needed to meet heat dissipation demands. Developing high-thermal-conductivity microwave dielectric ceramics with larger relative permittivity ( ε r ) would facilitate the miniaturization of high-power devices. Adding TiO 2 to the α-Al 2 O 3 matrix can adjust the temperature coefficient of resonant frequency ( τ f ) to near zero while increasing ε r , making it an effective approach to obtain high thermal conductivity and low-loss microwave dielectric ceramics. However, systematic defect analysis of the Al 2 O 3 –TiO 2 composition is still lacking. This work investigates the dielectric and thermal properties of the Al 2 O 3 –TiO 2 composition from a defect perspective. By combining low-frequency dielectric spectra with thermally stimulated depolarization current (TSDC) techniques, it was found that the solid solution of Al 3+ in the rutile TiO 2 phase suppresses the activity of defects such as oxygen vacancies. However, the introduction of Ti 4+ into the Al 2 O 3 phase introduces aluminum vacancies (