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Theoretical Study on Structure and Property of Binary Composite Oxide α-(Al1-xYx)2O3

Author: WangYanBo
Tutor: SongQingGong
School: Hebei University of Technology
Course: Theoretical Physics
Keywords: binary composite oxide first-principles crystal structure electronic structure mechanical properties
CLC: O469
Type: Master's thesis
Year: 2011
Downloads: 18
Quote: 0
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Abstract


In this paper, binary composite oxidesα-(Al1-xYx)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-(Al3/4Y1/4)2O3 andα-(Al1/4Y3/4)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-(Al3/4Y1/4)2O3 andα-(Al1/4Y3/4)2O3 are tentatively designed and their formation energy, electronic structure, populations were calculated and analyzed. The results show their structure’s stability andα-(Al1/4Y3/4)2O3 is more stable thanα-(Al3/4Y1/4)2O3. This may be suggesting a new type of promising material.The results show that YAG, YAP, YAM,α-(Al3/4Y1/4)2O3 andα-(Al1/4Y3/4)2O3 are insulators. In these binary composite oxides, bonds O-Al and O-Y are composed of stronger ionic bond and weaker covalent bond.

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