Acceptor doped BaZrO3 is the prototype of proton conducting perovskites which are of strong interest as electrolytes for intermediate temperature fuel cells. Elastic properties of both dry and hydrated Y-doped BaZrO3 (1.5–17 mol% Y) were determined using ultrasound time of flight (TOF) measurements, and complemented by ab initio calculations which allow for an analysis of the different contributions. The experimental and theoretical findings are consistent and reveal a strong decrease of the Young's, shear and bulk moduli upon increasing dopant concentration. This decrease is attributed to a combined effect of (i) macroscopic lattice chemical expansion mainly caused by differing ionic radii, and (ii) presence of point defects such as acceptors AccZr ′ (with decreased cation charge), oxygen vacancies VO ••, and protonic defects OHO • (hydroxide ions on oxide ion sites) that locally weaken the chemical bonds in the perovskite structure. The effect from modified lattice parameter is minor relative to the decrease in moduli caused by AccZr ′, VO ••, OHO • weakening the chemical bonds. The elastic moduli differ only slightly between the dehydrated and hydrated samples. The decrease in the elastic moduli with increasing acceptor and oxygen vacancy concentrations is much stronger in Y-doped BaZrO3 (−5.8% in Y:BaZrO3 per mol% of vacancies) compared to similar earlier investigations on Gd-doped CeO2 (−2% in Gd:CeO2). This result indicates a greater effect of oxygen vacancies on the elastic properties in ABO3 perovskites with the linear B–O–B bonds as compared to fluorites with strongly bent M-O-M bonds.
|Number of pages||10|
|State||Published - Nov 2018|
Bibliographical noteFunding Information:
Financial support by the German-Israeli Foundation for Scientific Research and Development (grant I-1342-302.5/2016 ) is gratefully acknowledged. The computer resources are provided by the Stuttgart Supercomputing Center (Project DEFTD 12939). This research was partly funded by the ERA-NET HarvEnPiez project (EK) . We thank Yuanye Huang and Armin Sorg (MPI-FKF) for assistance with powder preparation and spark plasma sintering, as well as Tor Bjorheim (University of Oslo), Eugene Heifets (Photochemistry Center, Russian Academy of Sciences), and David Fuks (Ben-Gurion University of the Negev) for fruitful discussions.
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