Theoretical Study On Structure And Property Of Binary Composite Oxide α-(Al_1-xY_x)₂O₃

In this paper, binary composite oxidesα-(Al_1-xY_x)₂O₃ are studied in order to explore new types materials with stable structure and comprehensive performance. This is of great importance for developing anti-oxidation materials as well as other functional materials.Twelve first principles calculation schemes based on density functional theory were designed and used to make calculation on three kinds of compoundα-Al₂O₃,α-Y₂O₃ and YAP (YAlO₃). It was found that the calculated results with GGA-PW91-On the fly scheme were mostly close to the reported experimental data. Accordingly, this scheme was employed to complete calculation on crystalsα-Al₂O₃,α-Y₂O₃, YAG (Y₃Al₅O₁₂), YAP (YAlO3), YAM (Y4Al₂O₉),α-(Al_3/4Y_1/4)₂O₃ andα-(Al_1/4Y_3/4)₂O₃.The formation energies, electronic structures, populations and mechanical properties of YAG and YAP were studied and the results indicate YAG and YAP are all of good structural stability and confirmed by other's experimental evidence. The analysis of the mechanical properties shows that YAG and YAP belong to the brittle material.The formation energies, electronic structures and populations of YAM were studied and the results show that YAM crystal is more stable thanα-Al₂O₃, YAG and YAP crystals.The structure models ofα-(Al_3/4Y_1/4)₂O₃ andα-(Al_1/4Y_3/4)₂O₃ are tentatively designed and their formation energy, electronic structure, populations were calculated and analyzed. The results show their structure's stability andα-(Al_1/4Y_3/4)₂O₃ is more stable thanα-(Al_3/4Y_1/4)₂O₃. This may be suggesting a new type of promising material.The results show that YAG, YAP, YAM,α-(Al_3/4Y_1/4)₂O₃ andα-(Al_1/4Y_3/4)₂O₃ are insulators. In these binary composite oxides, bonds O-Al and O-Y are composed of stronger ionic bond and weaker covalent bond.