Non-congruence of high-temperature mechanical and structural behaviors of LaCoO<inf>3</inf> based perovskites
1563 - 1576
Journal of the European Ceramic Society
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© 2016 Elsevier LtdThis paper presents the mechanical behavior of LaCoO3 and La0.8Ca0.2CoO3 ceramics under four-point bending in which the two cobaltites are subjected to a low stress of ∼8 MPa at temperatures ranging from room temperature to 1000 °C. Unexpected stiffening is observed in pure LaCoO3 in the 700–900 °C temperature range, leading to a significant increase in the measured Young's modulus, whereas La0.8Ca0.2CoO3 exhibits softening from 100 °C to 1000 °C, as expected for most materials upon heating. Neutron diffraction, X-ray diffraction and micro-Raman spectroscopy are used to study the crystal structure of the two materials in the RT–1000 °C temperature range. Despite a detailed study, there is no conclusive evidence to explain the stiffening behavior observed in pure LaCoO3 as opposed to the softening behavior in La0.8Ca0.2CoO3 at high temperatures (above 500 °C).