I've deposited REFeO3 thin film, with RE=La, Pr, Nd and Sm. I've performed 4-probes measurements, in range 400-600°C (intrinsic domain). As expected, smaller RE cation gives higher resistivity, but when I linearize the curve by Arrhenius Plot, I obtain decrease of activation energy with smaller RE.
It should suggest easier conduction mechanisms with smaller RE, but a higher resistivity. I have no explanation for that, and I need suggestion!
Could you please explain why higher resistivity is expected for smaller RE cations?
If the lattice parameter is smaller, then I think the Fe d-orbital overlap would increase, thereby lowering the activation energy of charge movement.
Dear Martin,
Thank you for your answer.
REFeO3 are orthorhombic perovskite, where FeO6 octahedra are stacking with an angle lower than 180°. By reducing the RE size, this angle decreases (in order to fill the space let by smaller RE), and should lead to lower overlapping between 3d Fe electron and 2p O electron, and must increase resistivity AND activation energy of charge movement. I arrive with opposite explanation than yours. But resistivity and activation energy go in opposite conclusions...
The reducing of the RE size would produce lattice distortion and point defects, which maybe change the carries concentration.
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