Influence of structural arrangement of R2O2 slabs of layered cuprates on high-temperature properties important for application in IT-SOFC

Abstract

Abstract Layered cuprates Pr2 − xSrxCuO4-δ with T* (x = 0.3, 0.4) and T (x = 1.0, 1.3) structures were prepared in air at 1273–1373 K. Oxygen content (4 − δ) of the as-prepared phases decreases from 3.96 (x = 0.3) and 3.98 (x = 0.4) to 3.69 (x = 1.0) and 3.49 (x = 1.3), respectively, as determined by chemical titration. Dilatometry measurements revealed non-linear expansion with low- and high-temperature regions occurring due to thermogravimetrically detected oxygen loss. Different expansion behaviors in low- and high-temperature regions of T- and T*-phases are attributed to various distributions of oxygen vacancies in their crystal structures. Both x = 0.4 and 1.0 ceramic samples exhibit lower conductivity values at high temperatures in comparison with undoped Pr2CuO4. The temperature dependences of the electrical conductivity at variable oxygen partial pressure ( p O 2 = 10− 4–0.21 atm) reveal different mechanisms of the holes generation in x = 0.4 and 1.0 compounds. The tracer diffusion coefficient of oxygen (DT) in Pr1.6Sr0.4CuO3.98 determined by isotopic exchange depth profile (IEDP) technique using secondary ion mass spectrometry (SIMS) is in the range 6.7 × 10− 10–5.7 × 10− 8 cm2/s at 973–1223 K. Obtained values are in between those for La2CuO4 and Pr2CuO4 with pure rock-salt and fluorite slabs in the crystal structure, respectively. This shows the importance of rock-salt slabs for high oxygen conductivity in R2MO4 oxides.