Atomic-scale structure-property relationship of ferroelastic LaCoO$^{3}$

The ferroelastic oxide LaCoO$^{3}$ has attracted increasing attention by exhibiting room-temperature creep, which is usually only observed at temperatures close to a material's melting point. To advance our understanding of these unusual properties, a combination of TEM techniques, including electron diffraction, atomic-resolution Z-contrast imaging and electron energy-loss spectroscopy have been used to study the LaCoO$^{3}$ microstructures as a function of applied strain. In polycrystalline samples compressed at room temperature above the coercive strain, we observed the formation of superlattice domains with lattice constant 3a$^{0}$, which have been attributed to monoclinic distortions within the rhombohedral lattice.$_{1}$ While in untreated LaCoO$^{3}$ and samples compressed below the coercive strain we only found twin boundaries within the grain. We will further show how these superstructure domains evolve as a function of time, and correlate the transformation of the monoclinic superlattice into highly twinned rhombohedral bulk to the room-temperature strain recovery observed in bulk LaCoO$^{3}$ after unloading.$_{2}$ $_{1--}$ J.C. Walmsley et al., J. Mat Sci, 35, 4251-60 (2000) $_{2}$ Funded by: NSF CAREER Award DMR-0846748