Non-congruence of high-temperature mechanical and structural behaviors of LaCoO₃ based perovskites

详细信息    查看全文

• 作者：Amjad Aman^a ; Ryan Jordan^a ; Yan Chen^a ; ^b ; Richard Stadelmann^a ; Mykola Lugovy^a ; ^c ; Nina Orlovskaya^a ; ^{Nina.Orlovskaya@ucf.edu} ; E. Andrew Payzant^b ; Clarina dela Cruz^d ; Michael J. Reece^e ; Thomas Graule^f ; Jakob Kuebler^f
• 关键词：Lanthanum cobaltite ; Powder diffraction ; Raman spectroscopy ; Young&rsquo ; s modulus ; Temperature dependence ; Hysteresis
• 刊名：Journal of the European Ceramic Society
• 出版年：2017
• 出版时间：April 2017
• 年：2017
• 卷：37
• 期：4
• 页码：1563-1576
• 全文大小：4319 K
• 卷排序：37

文摘

This 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).