Microstructural Characterization of High-Thermal-Conductivity Aluminum Nitride Ceramic

摘要

An aluminum nitride (AlN) ceramic with a thermal conductivity value of 272 W·(m·K)~(-1), which is as high as the experimentally measured thermal conductivity of an AlN single crystal, was successfully fabricated by firing at 1900℃ with a sintering aid of 1 mol% Y_2O_3 under a reducing N_2 atmosphere for 100h. Oxygen concentrations were determined to be 0.02 and 0.03 mass% in the grains and in the grain-boundary phases, respectively. Neither stacking fault in the grains nor crystalline phase in the grain-boundary regions was found by transmission electron microscopy. An amorphous phase possessing yttrium and oxygen elements was detected between the grains as thin films with a thickness of <1nm. Because the amount of grain-boundary phase was small, the high-thermal conductivity of the ceramic was attributable to the low oxygen concentration in the AlN grains.