WO3 ADDITION, CRYSTAL PHASE EVOLUTION AND PROPERTIES OF Y2O3-DOPED ALN CERAMICS

Abstract

The effect of WO3 addition on the densification, phase evolution, and properties of Y2O3-doped AlN ceramics sintered at 1800oC for 3 h was investigated. The total amount of oxides added was 4.5 wt. %. In all of the compositions investigated, YAlO3 and Y4Al2O9 were observed as the secondary phases. When WO3 was added, W2B was also identified. As the quantity of WO3 increased, the amount of YAlO3 and W2B increased and that of Y4Al2O9 decreased. However, the sinterability and thermal conductivity of the sintered body were not influenced much. The optical reflectance decreased from 25 to approximately 10 % in the visible-light regime, by the formation of W2B. For the sintered body with composition 3.5 Y2O3-1.0 WO3-95.5 AlN, the thermal conductivity, the elastic modulus, and the Poisson ratio were 134 Wm-1 K-1, 368 GPa and 0.196, respectively; and the dielectric constant and loss tangent at the resonant frequency of 8.25 GHz were 8.60 and 0.003, respectively.

Keywords

• Aluminum nitride
• WO3
• Optical reflectance
• Thermal conductivity
• Dielectric properties