96Zr Tracer Diffusion in AZrO3 (A = Ca, Sr, Ba)

Abstract

Cation tracer diffusion in polycrystalline AZrO 3 (A = Ca, Sr, Ba) perovskites was studied at 1300-1500 • C in air using the stable isotope 96 Zr. Thin films of 96 ZrO 2 were deposited on polished ceramic pellets by drop casting of an aqueous precursor solution containing the tracer. The pellets were subjected to thermal annealing, and the isotope depth profiles were measured by secondary ion mass spectrometry. Two distinct regions with different slopes in the profiles enabled to assess separately the lattice and grain boundary diffusion coefficients using Fick's second law and Whipple-Le Clair's equation. The cation diffusion along grain boundaries was 4-5 orders of magnitude faster than the corresponding lattice diffusion. The magnitude of the diffusivity of Zr 4+ was observed to increase with decreasing size of the A-cation in AZrO 3 , while the activation energy for the diffusion was comparable 435 ± 67, 505 ± 56, and 445 ± 45 and kJ·mol −1 for BaZrO 3 , SrZrO 3 , and CaZrO 3 , respectively. Several diffusion mechanisms for Zr 4+ were considered, including paths via Zr-and A-site vacancies. The Zr 4+ diffusion coefficients reported here were compared to previous data reported on B-site diffusion in perovskites, and Zr 4+ diffusion in fluorite-type compounds.

Effects of NiO addition on sintering and proton uptake of Ba(Zr,Ce,Y)O3−δ

“…The open symbols represent Ni-free samples from conventional sintering collected from literature. While the individual data have some scatter, the fitted activation energy of 3.7 eV agrees well to the activation energies of cation GB diffusion in BaZrO 3 (3.7 eV for Zr, 3.0 eV for Ba), 52,53 bulk activation energies amount to 4.5 eV for Zr, 4 eV for Ba). The activation energy increases to 5.3 eV for SSRS samples with 0.25 wt% NiO addition, and further increases to 6.2 eV with higher NiO content.…”

B-site cation inter-diffusion in yttrium substituted barium zirconate

“…Similar conclusions were made by Sazinas et al for nominal BZ and Vøllestad et al for cation diffusion in lanthanum tungstate. 4,20 Schultz et al obtained higher activation energies at higher temperatures than at lower temperatures in their tracer diffusion study of lanthanum gallate and explained it by a frozen in defect structure at the lower temperatures. 21 The inter-diffusion coefficients are systematically higher in reducing than oxidising atmosphere (see Figure 4 and Figure 6), whereas the activation energies are within the experimental uncertainty.…”

“…Sazinas et al studied cation diffusion in BaZrO 3 (BZ) and related perovskites experimentally. [4][5][6] They performed tracer diffusion experiments on BZ, determining the diffusion profiles by means of Secondary Ion Mass Spectrometry (SIMS). The activation energies of Ba and Zr tracer diffusion in BZ were estimated to be (4.1 ± 0.5) eV and (4.5 ± 0.7) eV, respectively.…”

Numerical Simulation of the SrZrO3 Formation in Solid Oxide Fuel Cells

“…Besides, the thermodynamic parameters for other phases are directly acquired form literature and no higher order parameter is adjusted to the ZrO2-CeO2-SrO system. The available elemental bulk diffusion coefficients are adopted from literature, including Ce in YSZ [27], Zr in YSZ [28], Sr in CGO [29] and Zr in SZO [30]. Due to lack of experimental data, it is assumed in the current work that the diffusivities of Zr and Ce in CGO are the same as those in YSZ.…”