Composite solid electrolytes based on CaZrO3 as components for electrochemical devices applied in metallurgy
Magdalena Dudek*, Grzegorz Róg*, Władysław Bogusz**, Mirosław M. Bućko***, Anna Kozłowska-Róg*** *Akademia Górniczo-Hutnicza, Wydział Inżynierii Materiałowej i Ceramiki, al. Mickiewicza 30, 30-059 Kraków **Politechnika Warszawska, Wydział Fizyki, Zakład Joniki Ciała Stałego, ul. św. Andrzeja Boboli 8, 02-524 Warszawa ***Akademia Górniczo-Hutnicza, Wydział Inżynierii Materiałowej i Ceramiki, al. Mickiewicza 30, 30-059 Kraków
Quarterly No. 4, 2005 pages 14-19
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abstract Non-stoichiometric calcium zirconate is one of the ion-conducting materials for high-temperature applications. Relatively low oxygen ion conductivity of pure CaZrO3 (10−6 S • cm−1 at 1000ºC) limits the practical use of such material as a solid electrolyte in the electrochemical devices applied in metallurgy. The aim of the present paper was to obtain composite ionic conductors in the two systems: calcium zirconate (CaZrO3) - tricalcium aluminate (Ca3Al2O6) and calcium zirconate - cubic solid solution CaO-ZrO2 as well as to investigate their electrical and mechanical properties. The composite materials were prepared by sintering of mechanically homogenized mixtures of the respective powders. In the case of the CaZrO3-Ca3Al2O6 samples changes of the lattice parameters of the respective phases suggested a chemical reaction between the components with formation of nonstoichiometric calcium zirconate. It was stated that a small additive of tricalcium aluminate, up to 2% mol., causes a significant increase (even 30 000 times when compare to the pure calcium zirconate matrix) of the electrical conductivity of the composites. Introduction of the calcia fully-stabilized zirconia inclusions into CaZrO3 matrix also leads to the improvement of the electrical properties of the composite materials. In all samples the oxygen ion transference number, estimated by the EMF method, appeared to be close unity. The introduction of the inclusions in the both sample series did not influence significantly a fracture toughness of the samples, expressed by KIC values. The preliminary results of reactivity between the CaZrO3 + 2% mol. Ca3Al2O6 sample and liquid copper and nickel showed that such composite could be applied as a solid electrolyte in electrochemical probes for determination of dissolved oxygen in molten metals. The prepared composite materials seems to be also promising solid electrolytes for galvanic cells to the determination of thermodynamic properties of intermetallic compounds, carbides and oxide systems having low oxygen partial pressures. Key words: calcium zirconate, ionic conduction, composite solid electrolytes, solid oxide cells