Yttrium doped barium zirconate, BaZr_1-xY_xO_3-δ, has been one of the most studied high temperature proton conductors for the last two decades [1]. Several research groups focused on the choice of the trivalent dopant, which is necessary to create the oxygen vacancies required for the hydration of the material. Han et al. studied for example Sc, Sm, Eu and Dy dopants [2-4] and reported the presence of Dy⁴⁺in oxidizing atmospheres.

In this work, we are interested in the comparison of structural and electrical properties between the well-known BZY10 (BaZr_0.9Y_0.1O_3-δ) and BZDy10 (BaZr_0.9Dy_0.1O_3-δ). A wide combination of experiments was used to confirm the presence of Dy⁴⁺ in oxidizing atmosphere, including high temperature X-ray diffraction, Raman spectroscopy, SQUID magnetometry and electron spin resonance (ESR or EPR). Figure 1 summarizes the BZDy10 lattice parameter in dry oxidizing atmosphere as a function of temperature and shows a decrease in the lattice parameter when increasing the oxygen partial pressure. This is explained by the difference in Dy radii in VI coordination: 0.78 Å and 0.912 Å for Dy⁴⁺ and Dy³⁺respectively.

Conductivity measurements as a function of pO₂in dry and moist conditions were performed for both BZY10 and BZDy10. The two materials behaved quite similarly in moist reducing atmosphere (i.e., pure ionic conduction), while significant differences were noticed in oxidizing atmospheres.

[1] Fabbri E., Pergolesi D. and Traversa E., “Materials challenges toward proton-conducting oxide fuel cells: a critical review ”, Chem. Soc. Rev 39, 4355-4369 (2010)

[2] D. Han, K. Shinoda, T. Uda, Dopant site occupancy and chemical expansion in rare earth-doped barium zirconate, J. Am. Ceram. Soc. 97 (2014) 643-650

[3] D. Han, T. Uda, Y. Nose, T. Okajima, H. Murata, I. Tanaka and K. Shinoda, Tetravalent Dysprosium in a Perovskite-Type Oxide, Advanced Materials 24 (2012) 2051-2053

[4] D. Han, K. Shinoda, S. Sato, M. Majima, T. Uda, Correlation between electroncutive and structural properties of proton conductive acceptor doped barium zirconate, J. Mater. Chem. A, 13 (2015) 1243-1250