Space–charge theory applied to the grain boundary impedance of proton conducting BaZr0.9Y0.1O3−δ.

Christian Kjølseth (1) , Harald Fjeld (1) , Øystein Prytz (2) , Paul Inge Dahl (3) , Claude Estournès (4) , Reidar Haugsrud (1) , Truls Norby (1)

1 Department of Chemistry [Oslo]
2 Department of Physics [Oslo]
3 IMA NTNU - Department of Materials Science and Engineering [Trondheim]
4 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux

The specific grain interior and grain boundary conductivities, obtained from impedance spectroscopy and the brick layer model, are reported for BaZr0.9Y0.1O3−δ as a function of pO2 and temperature. pO2-dependencies were indicative of dominating ionic and p-type electronic conduction for the grain interior under reducing and oxidizing conditions, respectively, while the grain boundaries showed an additional n-type electronic contribution under reducing conditions. Transmission electron microscopy revealed enrichment of Y in the grain boundary region. These findings indicate the existence of space–charge layers in the grain boundaries. A grain boundary core–space–charge layer model is therefore applied to interpret the data. Using a Mott–Schottky approximation, a Schottky barrier height of 0.5–0.6 V and an effective grain boundary width of 8–10 nm (=2× space–charge layer thickness) is obtained at 250 °C in wet oxygen. Finite-element modelling of the complex impedance over a grain boundary with a space–charge layer depletion of protons yields a distorted semicircle as observed in the impedance spectra.

Mots clés: BaZrO3; BaZr0.9Y0.1O3−δ; Proton conductivity; Grain boundary resistance; Impedance spectroscopy; Space–charge layer

Domaines: Matériaux

Christian Kjølseth, Harald Fjeld, Øystein Prytz, Paul Inge Dahl, Claude Estournès, et al.. Space–charge theory applied to the grain boundary impedance of proton conducting BaZr0.9Y0.1O3−δ.. Solid State Ionics, 2010, 181 (5-7), pp.268-275. ⟨10.1016/j.ssi.2010.01.014⟩. ⟨hal-03556896⟩