Reducing the chemical expansion coefficient in ceria by addition of zirconia

For the first time, the role of isovalent Zr substitution in cerium oxide on the non-stoichiometry induced dilation (chemical expansion) was investigated. Chemical expansion was derived experimentally using HTXRD, dilatometry, and TGA measurements on Pr_0.1Zr_0.4Ce_0.5O _1.95-δ and computationally with DFT calculations on Zr _0.5Ce_0.5O_2-δ. Though Zr was found to increase the reducibility and the corresponding chemical expansion of ceria in the studied range, the relationship between chemical expansion and non-stoichiometry (the chemical expansion coefficient) was significantly smaller (54% less) than that observed in ceria, and consistent with predictions from the authors' previous work. The origin of the reduced chemical expansion coefficient, associated with a larger contraction of the lattice around oxygen vacancies, is explained using DFT calculations and corroborated with prior investigations of enhanced reducibility of ceria-zirconia. Additionally, implications of this discovery for solid oxide fuel cells and heterogeneous catalyst systems are also discussed.