Proton Conductivity of La2(Hf2−xLax)O7−x/2 “Stuffed” Pyrochlores

Applied Sciences

Dmitry N. Stolbov¹  Dmitry A. Medvedev²  Anna V. Kasyanova²  Nikolay V. Lyskov³  Galina E. Nikiforova⁴  Anna V. Shlyakhtina⁵  Igor V. Kolbanev⁵  Galina A. Vorobieva⁵ 

[1] Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia;Institute of High Temperature Electrochemistry, Ural Branch, Russian Academy of Sciences, 620219 Ekaterinburg, Russia;Institute of Problems of Chemical Physics RAS, Moscow Region, 142432 Chernogolovka, Russia;Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 119991 Moscow, Russia;N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia;

关键词: SOFCs;    hafnates;    solid oxide electrolytes;    ionic conductivity;   

DOI  :  10.3390/app12094342

来源: DOAJ

【 摘 要 】

The design of new oxygen- and proton-conducting materials is of paramount importance for their possible utilization in solid oxide fuel cells. In the present work, La₂(Hf_2–xLa_x)O_7–x/2 (x = 0, 0.1) ceramics were prepared using ball milling of oxide mixtures (La₂O₃ and HfO₂) followed by high-temperature annealing at 1600 °C for 10 h in air. La₂Hf₂O₇ ceramics exhibit an ordered pyrochlore-type structure, whereas La₂(Hf_1.9La_0.1)O_6.95 has a defect pyrochlore structure type with oxygen vacancies at the 48f positions. The oxygen ion and proton conductivity of La₂(Hf_1.9La_0.1)O_6.95 “stuffed” pyrochlore ceramics was investigated by electrochemical impedance spectroscopy (two-probe AC) and four-probe DC measurements in a dry and a wet atmosphere (air and nitrogen). The use of two distinct conductivity measurement techniques ensured, for the first time, the collection of reliable data on the proton conductivity of the La₂(Hf_1.9La_0.1)O_6.95 “stuffed” hafnate pyrochlore. La₂Hf₂O₇ was found to be a dielectric in the range 400–900 °C, whereas the La₂(Hf_1.9La_0.1)O_6.95 “stuffed” pyrochlore had both oxygen ion and proton conductivities in this temperature range. The proton conductivity level was found to be equal to ~8 × 10⁻⁵ S/cm at 700 °C. Clearly, the proton conductivity of the La₂(Hf_1.9La_0.1)O_6.95 “stuffed” hafnate pyrochlore is mainly due to the hydration of oxygen vacancies at 48f positions.

【 授权许可】

Unknown