Transmission electron microscopy (TEM) studies of films prepared in the AlN-Al2O3 pseudobinary system by chemical vapor deposition (as described in a companion paper entitled, "Chemical Vapor Deposition of AlxOyNz Films") indicates that four different phases can be obtained by altering the NH3/CO2 gas ratio and preparation temperature. Films prepared at 900°C yield three polycrystalline phases and an amorphous composition. From zero to 25 at. percent O an AlN phase is observed. Amorphous material is observed from 25 to 47 at. percent O. From 47 to 59 at. percent O an AlxOyNz spinel is observed. At 60 at. percent O (pure Al2O3) an alumina phase is observed (KI phase). For 770°C films the AlN phase is observed from zero to 8 at. percent 0; from 8 to 23 at. percent O the zeta-alumina phase is seen; and at 60 at. percent O the KI alumina phase is again observed. For both the 770 and 900°C films, the grain size of the AlN phase was found to decrease with increasing oxygen content. Direct current-voltage, dielectric breakdown and capacitance-voltage measurements were performed on the 900 and 770°C films with a variety of film compositions. For pure AlN and Al2O3, current-voltage and dielectric breakdown measurements correlate with the grain size observed by TEM. A maximum in breakdown field was observed for 900°C films at the composition which yielded minimum grain size of the AlN phase. A similar maximum is observed for the zeta-Al2O3 phase of the 770°C films. Positive flatband voltages and hysteresis of the capacitance-voltage trace was observed for most samples. Dielectric constants greater than 8 have been observed for some compositions. Several compositions appear to be attractive candidates for charge storage layers in MIOS devices. © 1975 American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.