In Situ TEM Temperature Study of Solid State Reaction of Lanthanum Oxide and Chromia

Rare earth elements like La and Ce are known to improve the corrosion resistance of coated ferritic steels [1, 2]. The solid state reaction between La-rich oxide and Cr₂O₃ has been studied by x-ray diffraction (XRD) and in situ heating TEM with electron diffraction. The La-rich oxide powder was found to be porous and polycrystalline and would start by healing the pores and forming a transition phase of orthorhombic CrLaO₃ [3] before migration of La is found at the interfaces (Figure 1). After full reaction pure La₂O₃ has been observed by HRTEM in a region initially starting as porous La-rich oxide (Figure 2).

1.            S. Canovic, et al., Oxidation of Co- and Ce-nanocoated FeCr steels: A microstructural investigation. Surface & Coatings Technology, 2012.

2.            M.W. Lundberg, et al., Precoated AISI441 for SOFC interconnectors studied by TEM methods. ECS Transactions, 2013. 57(1): p. 2321-2329.

3.            C.P. Khattak and D.E. Cox, Structural Studies of the (La,Sr)CrO₃ System. Materials Research Bulletine, 1977. 12: p. 463-472.