Diffuse Reflectance Infrared Fourier Transform Spectroscopy of Commercial MN Powders in Vacuum up to 700°C

AIN powders produced via three major industrial processes, i.e., chemical vapor deposition (CVD) from triethyl aluminum, carbothermnal reduction and nitridation of alumina, and direct nitridation of aluminum, are analyzed by using diffuse reflectance infrared Fourier transform spectroscopy with in situ heating in vacuum up to 700°C. Powders from the CVD and direct nitridation processes showed OHs over tetrahedrally coordinated Al ions (Al^sup IV^) above 250°C, indicating a boehmite (AlOOH)-like surface oxide structure on the surfaces of original powders, while the powder from the carbothermal process did not present an apparent Al^sup IV^ -OH band, implying a 0-Al^sub 2^O^sub 3^-like surface oxide structure. The bands at 2245 and 2120 cm^sup -1^ appearing above 200°C, which were not identified previously, might be assigned to cyanato and cyano groups, respectively. [PUBLICATION ABSTRACT]