Grain Boundary Phase Analysis for Y sub(2)O sub(3)-Doped AlN Ceramics

Y sub(2)O sub(3) is a common sintering additive of AlN ceramics to achieve densification and remove the oxygen impurity, resulting in a typically grain boundary phase (GBP) Y sub(3)Al sub(5)O sub(12) (YAG). Two AlN ceramics with 3wt% and 5wt% Y sub(2)O sub(3) intended for thermal conductivity study were sintered at 1800 [degrees]C for 4h. X-ray diffraction (XRD) indicates that GBP could either be YAG or YAP (YAlO sub(3)) phase, while the selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) in TEN identifies it as YAP instead of YAG. The electron back-scattering diffraction (EBSD) in SEN further confirms the general presence of YAP phase in both samples. In meanwhile, two types of Al-rich GBPs were also detected by TEN, which could account for extra dopant in the microstructure. GBP contents in the both samples were quantified by K-va lue method (XRD) and from backs catte red electron images. Such analyses of GBPs are helpful to understand the sintering mechanism and evaluate their contribution to the thermal conductivity of AlN.