Phase Stability and Mechanical Properties of α-(Al, Cr, Fe)2O3 Phase by First-principles Calculation

Comparable study regarding cell volume, binding energy, total electronic density, and mechanical properties were carried out for alpha-Al2O3, alpha-(Al0.75Cr0.25)(2)O-3, alpha-(Al0.75-x Cr0.25Fex)(2)O-3, and alpha-(Al0.75Cr0.25-xFex)(2)O-3 phases using first principles calculation. The results show that the volume of alpha-(Al0.75-xCr0.25Fex)(2)O-3 phase increases with the increasing Fe substitution of Al, while the volume of alpha-(Al0.75Cr0.25-xFex)(2)O-3 phase decreases as Fe content increases.The binding energy indicates that all the phases, including alpha-Al2O3, alpha-(Al0.75Cr0.25)(2)O-3, alpha-(Al0.75-xCr0.25Fex)(2)O-3, and alpha-(Al0.75Cr0.25-xFex)(2)O-3 phases, are stable, among which alpha-Al2O3 is the most stable phase, whereas the stability decrease as the number of impurity atom increases. An increase of hardness, H/E and H-3/E*(2) is detected for both alpha-(Al0.75-xCr0.25Fex)(2)O-3 and alpha-(Al0.75Cr0.25-xFex)(2)O-3 phases compared with alpha- (Al0.75Cr0.25)(2)O-3 phase as determined by the increasing amount of Fe atoms with a range of 0-3 at. %. All the phases including alpha-(Al0.75Cr0.25)(2)O-3, alpha-(Al0.75-xCr0.25Fex)(2)O-3,and alpha-(Al0.75Cr0.25-xFex)(2)O-3 show lower mechanical properties compared to alpha-Al2O3 phase except for the alpha-(Al0.63Cr0.25Fe0.12)(2)O-3 phase that have higher H/E and H-3/E*(2).