Ceramics-Silikáty 58 (2) 132-137 (2014)

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

The effect of WO₃ addition on the densification, phase evolution, and properties of Y₂O₃-doped AlN ceramics sintered at 1800°C 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