HRTEM observations of La2Zr2O7 thin layers on LaAlO3 obtained by chemical methods

La2Zr2O7 (LZO) films have been grown by metalorganic Decomposition (MOD) to be used as buffer layers for coated conductors. LZO can crystallize into two similarstructures: fluorite or pyrochlore. Coated conductor application focuses on pyrochlore structure because it is a good barrier against oxygen diffusion. Classical X-ray diffraction is not able to separate the contribution of these two structures. TEM and HRTEM were used to determine the local distribution of these two phases in epitaxial LZO layers grown on LaAlO3. A characteristic feature of LZO thin films deposited by MOD is the formation of nanovoids in an almost single crystal structure of LZO pyrochlore phase. Forcomparison, LZO layers deposited by Metalorganic Chemical Vapor Deposition (MOCVD) were also studied. In this last case, the film is compact without voids and thestructure corresponds to pyrochlore phase. Thus, the formation of nanovoids is a characteristic feature of MOD grown films.