Monoclinic Ferroelastic Domains in LaCoO₃‐Based Perovskites

Abstract

LaCoO 3 -materials have received considerable attention due to their novel magnetic properties [1][2][3] and mixed ionicelectronic conductivity at elevated temperatures leading to exciting applications such as electrodes in solid oxide fuel cells [4] and oxygen permeable membranes.[5] Perovskites such as LaCoO 3 and related materials like LaAlO 3 undergo a displacive phase transition from a paraelastic cubic perovskite with space group Pm 3m at high temperatures to a ferroelastic rhombohedral perovskite with space group R 3c. [6][7][8][9][10] Toughening of the materials is particularly beneficial for membrane applications. Ferroelastic domain switching in LaCoO 3 -materials under mechanical load may increase the fracture toughness of the materials.[11] Microstructure investigations of the ferroelastic domains and switching mechanisms in LaCoO 3 -materials are therefore interesting in order to understand the materials′ mechanical behavior. In this work we report a detailed transmission electron microscopy (TEM) analysis of the ferroelastic domains in LaCoO 3 -based materials. In addition to the well known ferroelastic domains formed by deformation twinning in rhombohedral perovskites, a monoclinic structure is observed by TEM in LaCoO 3 -based materials. The second order improper paraelastic to ferroelastic phase transition in LaCoO 3 -materials doubles the periodicity along the threefold axis, which becomes the unique axis of the rhombohedral ferroelastic state. The phase transition results in the well known deformation twinning (ferroelastic twin domain [12]

Origin of the net magnetic moment in LaCoO3

“…[15,29,30] Thermal conductivity and electrical resistivity also undergo interest- ing changes in the 10K < T < 300K region. [31,25,32,33] Possible sources of magnetic moment are the twinning interfaces that appear in the bulk LCO [34,5,35] and possibly in nanoparticles. Putting strain on thin LCO films can create such interfaces near the substrate interface.…”

Symmetry‐Driven Atomic Rearrangement at a Brownmillerite–Perovskite Interface

“…Thanks to the advancements in imaging techniques over the past several decades, the structural components contributing to these interfacial phenomena can be identified and used in the interpretation of new nanoscale behavior. [25][26][27][28] In this work, we probe the microstructure of epitaxial SCO films grown on STO substrates using scanning transmission electron microscopy (STEM), which can reveal the influence of symmetry mismatch-driven strain upon the interfacial architecture. Using geometric phase analysis [29,30] (GPA), we carefully mapped out the strain-variation existing between two different domain structures.…”

Anelastic properties of La0.6Sr0.4Co1−Fe O3- at high temperatures

“…From these results, it is suggested that the rhombohedral LSCF is not ideally elastic and the decrease in the elastic modulus of LSCF is related with nonelastic effects. Furthermore, the rhombohedral LSCF is known to show ferroelastic behavior [9][10][11] . The rhombohedral crystal structure of LSCF is formed by the compression of the ideal cubic structure along the <111> directions of a cubic unit cell.…”