Atomistic mechanisms that determine atomic coordination and local concentration of dopants at Σ5 (310)/[001] symmetric tilt grain boundaries in Y2O3-doped ZrO2 were analyzed using atomistic simulation techniques. Segregation mechanisms were found to be different from those in metals or metalloids, with local strain relief controlled by short-range interactions, which act as the driving force for segregation, while long-range Coulombic interactions between the grain boundary region and the dopants resist segregation. It was found that Y3+ ions segregate to a region within around 0.6nm either side of the grain boundary plane. The equilibrium local concentration of dopants in the vicinity of the grain boundary, which was determined by the balance between repulsive forces between dopants and the grain boundary and attractive forces associated with local strain relief, was calculated to be 16.7mol% for 10.3mol%Y2O3-doped ZrO2. Co-segregation of an O2– vacancy was necessary in order to accommodate a Y3+ ion at the Σ5 grain boundary; O2– vacancies played important roles in reducing the repulsion between dopants and the grain boundary and further relieving local strain. These conclusions were supported by Monte Carlo simulations, using an unrestricted model. Segregation-induced modifications to the grain boundary structure observed in the simulations were used to interpret experimental HREM and Z-contrast images.

Numerical Analysis of Solute Segregation at Σ5 (310)/[001] Symmetrical Tilt Grain Boundaries in Y2O3-Doped ZrO2. T.Oyama, M.Yoshiya, H.Matsubara, K.Matsunaga: Physical Review B, 2005, 71[22], 224105 (11pp)