Improved preparation of La1−xMexCoO3−δ (Me = Sr, Ca) and analysis of oxide ion conductivity with ion conducting microcontacts

✍ Scribed by W. Zipprich; S. Waschilewski; F. Rocholl; H.-D. Wiemhöfer

• Book ID: 104296680
• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 749 KB
• Volume: 101-103
• Category: Article
• ISSN: 0167-2738
• DOI: 10.1016/s0167-2738(97)00164-1

✦ Synopsis

Preparation

and ionic conductivity of the mixed conducting perovskites La,_,Me,CoO,_, with Me = Sr, Ca were investigated in the composition range x = 0.1-0.5. Two preparation methods, the first via metal complexes in aqueous solution and the second based on a spray-freezing/freeze-drying process, were studied with an emphasis on lower reaction temperatures for the formation of perovskite type oxides. Oxygen ion conductivities were measured as a function of composition x and temperature (55O"C-750°C) using oxygen ion conducting microcontacts (made of stabilised zirconia, contact radius in the range lo-80 p,m). Evaluation of the steady-state current voltage curves (slope, curvature) yields the oxygen ion conductivity as a function of the oxygen partial pressure. For all investigated compositions of Sr and Ca substituted perovskites, oxygen transport occurs by a vacancy mechanism. For instance, values of the ionic conductivities are 4.6 X 10m5 @cm))' for La, ,Sr,,CoO,_, and 2.8 X 10e5 @cm)-' for La, ,Ca,,CoO,_, at 700°C in air increasing by nearly a factor of ten with increasing Sr or Ca concentration.