A stabilization mechanism for the perovskite La2/3TiO3 compound with Fe2O3: A structural and electrical investigation

作者：Skapin, Sreco Davor; skapin, Andrijana Sever; Suvorov, Danilo; Gaberscek, Miran^*

来源：Journal of the European Ceramic Society, 2008, 28(10): 2025-2032.

DOI：10.1016/j.jeurceramsoc.2007.12.036

• perovskites
• solid solution
• defects
• electrical conductivity
• fuel cells
• La2/3TiO3

We have stabilized the perovskite La2/3TiO3 by adding LaFeO3 and shown that in general the stabilization mechanism for the (1 - x)La2/3TiO3-xLaFeO3 mixture involves the formation of a solid solution for compositions with x >= 0.04. The crystal structure of the solid solution transforms from orthorhombic to tetragonal at x = 0.2, becomes cubic in the range 0.3 < x < 0.8, and transforms again into orthorhombic (typical for pure LaFeO3) for values greater than 0.8. Detailed impedance-spectroscopy measurements for various compositions and conditions showed that the limiting step in the conduction mechanism was conduction across the grain boundaries. In the concentration range 0.04 <x < 0.25 the room temperature conductivity increases up to 0.0017 S cm(-1), after which it decreases again. Part of the initial increase is probably due to the formation of free electrons in accordance with (Fe-Ti,)' -> (Fe-Ti)(x) + n'. Other defect-formation mechanisms are also discussed, but are ruled out for a variety of reasons. Another interesting phenomenon that also affected the average conductivity was identified, i.e., the variation of the average particle size with composition.

• 出版日期2008