ANALYSIS OF SURFACE-STATE AND STABILITY DURING STORAGE OF AIN POWDERSBY X-RAY PHOTOELECTRON-SPECTROSCOPY

The surface state of as-prepared AIN powders produced by direct nitrid ation and carbothermal methods was characterized by X-ray photoelectro n spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XA ES), In the as-prepared AlN powders, small peaks assigned to imide and amide groups were detected in the N1s XPS spectra of directly nitride d powders but not in those of the carbothermally treated powders. Both an oxidized surface phase and a parent AIN phase could be distinguish ed in the A12p XPS and Al (KLL) XAES spectra of all the samples. The s tructural state of the oxidized surface phase was found to be similar to gamma-Al2O3. The average thickness of the oxidized surface phase wa s determined to be about 0.5-0.6 nm in directly nitrided AlN powders w hereas it was 1.1 nm in carbothermally treated AIN powders. The thickn ess of the oxidized surface phase increased with increasing storage ti mes of the AIN powders in a container under ambient atmosphere. The in crease of thickness with storage time of the oxidized surface phase in directly nitrided AlN powder was faster than in the carbothermally tr eated AIN powder. The oxidized surface phase changed from gamma-Al2O3 in the as-prepared AlN powders to a hydroxide phase during storage.