Phase separation and microstructural evolution of the perovskite and pyrochlore structures in Pb-based multi-cation complex Oxides: A transmission electron microscopy study

Abstract

Multi-cation perovskite thin films are attracting significant research attention, owing to their unique physical properties. In particular, studies that provide insight into the microstructural properties and growth mechanisms of multi-cation Pb-based complex oxide thin films are highly desirable. The microstructural properties of Pb- based complex oxide thin films were studied using various transmission electron microscopy (TEM) techniques. The pyrochlore structure was elucidated by studying the atomic structure using HR (high-resolution) TEM, fast Fourier transform, and HR high-angle annular dark-field scanning transmission electron analyses. Additionally, the chemical properties of the multi-cation sites were characterized by energy-dispersive X-ray spectrometry, whereby the chemical composition of the pyrochlore structure was identified as Pb2(Nb0.56Zr0.77Ti0.67)O7 and that of the perovskite structure as Pb(Nb0.4Zr0.3Ti0.3)O3. The specific orientation relationship, [110]Pyrochlore//[010]Perovskite and (220)Pyrochlore//(100)Perovskite, was confirmed between the pyrochlore and perovskite structures at the bottom area of the layer. However, tilting of the pyrochlore- structured grains was frequently observed with increasing thickness. Finally, recovery of the interplanar spacings was observed in the perovskite and pyrochlore phases.