Atomistic modeling of La³⁺ doping segregation effect on nanocrystalline yttria-stabilized zirconia

Abstract

The effect of La3+ doping on the structure and ionic conductivity change in nanocrystalline yttria-stabilized zirconia (YSZ) was studied using a combination of Monte Carlo and molecular dynamics simulations. The simulation revealed the segregation of La3+ at eight tilt grain boundary (GB) structures and predicted an average grain boundary (GB) energy decrease of 0.25 J m-2, which is close to the experimental values reported in the literature. Cation stabilization was found to be the main reason for the GB energy decrease, and energy fluctuations near the grain boundary are smoothed out with La3+ segregation. Both dynamic and energetic analysis on the Σ13(510)/[001] GB structure revealed La3+ doping hinders O2- diffusion in the GB region, where the diffusion coefficient monotonically decreases with increasing La3+ doping concentration. The effect was attributed to the increase in the site-dependent migration barriers for O2- hopping caused by segregated La3+, which also leads to anisotropic diffusion at the GB.

Molecular dynamics study of oxygen-ion diffusion in yttria-stabilized zirconia grain boundaries

“…The average anion/cation stoichiometry for 8YSZ is 1.93; at the GB core, the measured stoichiometry is 1.88, proving the deficiency of O 2− and consequently, segregation of V O at the GB core. These results agree with previous works, 19,68 and are likely responsible for the predicted space-charge regions due to V O and possibly Y 3+ segregation at the GB core and their depletion in the adjacent bulk regions. 69,70…”

“…8 Over the past 40 years, MD techniques have been mainly applied to simulate the oxygen-ion transport in high symmetry tilt or twist grain boundaries of commonly used solid oxide fuel cells (SOFCs) electrolytes. 9–21 However, since the majority of boundaries found in polycrystalline samples are a mix of twisted and tilted denominations-commonly named as “mixed,” “general,” or “random” GBs, 22–25 identifying pathways to enhance ion transport through mixed GBs is essential to improve oxygen-ion conductors' performance substantially. Therefore, in this study, an in-depth MD analysis was conducted to investigate the role of mixed GBs in well-known yttria-stabilized zirconia (YSZ) electrolytes.…”

Effect of Rare Earth Elements on Stability and Sintering Resistance of Tetragonal Zirconia for Advanced Thermal Barrier Coatings

“…The binding energy increases with the decrease of the Y 3+ -V O distance until the Vo occupied the second nearest neighbor site of the Y 3+ ion. The smallest energy difference was −0.474 eV, which shows a good agreement with the references' reports [31]. The Y 3+ ion with a large ionic size (compared with Zr 4+ ) preferred to have eight neighboring oxygen ions, whereas the Vo tended to occupy the nearest neighbor site of the Y 3+ ion.…”

Influence of La3+induced defects on MnO2–carbon nanotube hybrid electrodes for supercapacitors

“…Higher diffusion coefficient value of D=4.27 x10 -8 cm 2 /s for the 2La-MnO 2 -CNTelectrode was obtained as compared to that for 0La-MnO 2 -CNTsample (D= 9.49 x10 -9 cm 2 /s) which can be ascribed to the increase in mobility of electrolyte ions into the active electrode material due to the introduction of La 3+ dopants. Beyond 2 mol% La doping, the diffusion coefficient was found to decrease which might be due to the of aggregates of amorphous La(OH) 3 hindering the diffusion of electrolyte ions into the pores of the electroactive material [26,[44][45]…”