Article ID Journal Published Year Pages File Type
1476536 Journal of the European Ceramic Society 2008 8 Pages PDF
Abstract

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 (FeTi)′ → (FeTi)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.

Related Topics
Physical Sciences and Engineering Materials Science Ceramics and Composites
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