COMPOSITE OXIDE ELECTROLYTES FOR ELECTROCHEMICAL DEVICES

This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes, providing a brief overview of the materials having better performance than monophase ones in various high temperature electrochemical devices such as: solid oxide fuel cells, sensors for automotive industry, oxygen probes for controlling metal processing. Introduction of Al2O3 inclusions into cubic yttria - zirconia solid solution (8YSZ) matrix, caused the improvement of electrical and mechanical properties compared to pure 8YSZ. The Nd2Ti2O7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness KIc of 8YSZ ceramics was also significantly improved by Nd2Ti2O7 addition. Heterophase oxide ionic conductors in the system Calcium zirconate - cubic calcia zirconia solid electrolytes seem to be promising solid electrolytes for application in electrochemical probes for controlling oxygen dissolved in molten steel. The ionic conduction limit for electrolytes based on CaZrO3 is lower than that for calcia - stabilized zirconia (13CSZ). Hence CaZrO3-based materials perform better at low oxygen concentration at molten alloys. On the other hand composite layered ceramics involving Ce0.8Sm0.2O2/Bi(0.8)Eb(0.2)O(2) or Ce0.9Gd0.1O2/BaCe0.8Y0.2O3/Ce0.9Gd0.1O1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600 - 800 degrees C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance.