Abstract

The effects of Dy₂O₃ on the phase composition, microstructure, and the dielectric property, especially, dielectric constant, of AlN ceramics sintered at low-temperature (1650^oC), were investigated systematically. X-ray diffraction (XRD) was employed to indentify the phase compositions of the ceramics during the sintering. Scanning electronic microscopy (SEM) was used to observe the microstructures of the AlN ceramics. The results show that the dielectric constant changes with the amount of Dy₂O₃. When the amount of Dy₂O₃ is less than 0.93 wt.%, the dielectric constant increases with the increased amount of Dy₂O₃. The dielectric constant of the AlN ceramics is higher than 200 when the amount of Dy₂O₃ is 0.93 wt.%. However, when the amount of Dy₂O₃ is more than 0.93 wt.%, the dielectric constant decreases with the increased amount of Dy₂O₃. The dielectric constant of the AlN ceramics with 1.87 wt.% Dy₂O₃ is only about 15, which closed to the theoretical value of pure AlN ceramics. The analysis illuminated that the grain phases changed from Al₂O₃-rich aluminate to AlDyO₃ which existed at triple pockets with the increased amount of Dy₂O₃, the former can improve the dielectric constant greatly due to ion relaxation polarization.

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