Theoretical study on proton diffusivity in Y-doped BaZrO₃ with realistic dopant configurations

Abstract

The effect of dopant configurations on the proton diffusivity in yttrium-doped barium zirconate (BZY).

Probing Local Environments of Oxygen Vacancies Responsible for Hydration in Sc-Doped Barium Zirconates at Elevated Temperatures: In Situ X-ray Absorption Spectroscopy, Thermogravimetry, and Active Learning Ab Initio Replica Exchange Monte Carlo Simulations

“…The fractions approach the values for the random distribution of cations (60, 35, and 5% for the Zr–Zr, Sc–Zr, and Sc–Sc pairs, respectively) with increasing temperature, although the distribution is not yet completely random at a sintering temperature of 1627 °C (The situation is quite different in 30 at % Y-doped barium zirconate, for which the fraction of Y–Y pairs is 28%, much higher than that for a statistical random cation distribution at 1600 °C). In step 2, a special representative structure − that matches the averaged 2, 3, and 4-body correlation functions of the AL-RXMC samples from step 1 was generated at each temperature (red symbols in Figure S2). In the final step 3, AL-RXMC sampling of oxygen vacancy and proton configurations at thermal equilibrium were performed at 0, 33, 66, and 100% hydration (100% hydration corresponds to the composition where all oxygen vacancies are filled by oxide ions with a proton concentration of 0.222 per formula unit), while keeping the cation arrangement fixed to the single representative structure determined at 1627 °C in step 2 [To estimate whether equilibrium can be reached within the experimental conditions, we calculated the diffusion lengths of oxide ions from the reported activation energy of 89 kJ/mol and Arrhenius pre-factor of 3.40 × 10 –5 cm 2 /s for Y-doped barium zirconate (Sc-doped barium zirconate has not been reported).…”

Dopant-induced changes of local structures for adjusting the hydration ability of proton-conducting lanthanum scandates

“…51 At low temperatures, the change in DH 0 hydr is associated mainly with two opposite effects: the interaction of defects and trap-site lling. 52,53 The interaction of proton defects under conditions close to hydration saturation can prevent the complete hydration of the material. 54 In the case of a low dopant concentration, the number of traps (all oxygen atoms near the dopant atoms) signicantly exceeds the number of protons, so the trap-site lling effect should not be expected.…”

Incorporation of protons and hydroxide species in BaZrO3 and BaCeO3

“…For more accurate treatments of proton-dopant interactions in BZO, we refer the reader to other computational studies focused specifically on this problem, which employ larger supercells to capture varied dopant configurations. 56,57 To begin, we calculate barriers for H + i migration. We consider two pathways, summarized visually in Fig.…”