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

• Layered cuprates Pr2 - xSrxCuO4-delta with T* (x = 0.3, 0.4) and T (x = 1.0, 13) structures were prepared in air at 1273-1373 K. Oxygen content (4 - delta) of the as-prepared phases decreases from 3.96 (x = 03) 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 (Po-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 (D-T) 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 x 10(-10)-5.7 x 10(-8) cm(2)/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.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Layered cuprates

Thermal expansion

Oxygen diffusion

Cathode materials

High-temperature conductivity

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