Time dependent deformation of LaCoO₃ based perovskites at different temperatures: ferroelastic and non-ferroelastic creep behaviour

ABSTRACT

Analysis of the creep behaviour of ferroelastic LaCoO₃ and La_0.8Ca_0.2CoO₃ perovskites at room and elevated temperatures is presented. It was found that the creep behaviour of the two LaCoO₃-based compositions was determined by ferroelastic and non-ferroelastic creep strain components. Both the ferroelastic and non-ferroelastic creep strain components showed a strong dependence on bending stress. The ferroelastic creep depends on the coercive stress in LaCoO₃ based perovskites, which in turn is a function of temperature. In addition, the ferroelastic creep strain has the same sign as the total strain of cobaltites upon loading, however, it has the opposite sign relative to the total strain upon unloading. Non-ferroelastic creep was negligibly small in both perovskites at low temperatures, however, its contribution toward the total creep increased significantly at elevated temperature. Non-ferroelastic creep strain has the same sign as the total strain both upon loading and upon unloading.

KEYWORDS:

• Perovskite
• ferroelastic creep
• non-ferroelastic creep
• coercive stress
• bending

Acknowledgements

Dr. Lugovy’s work at Empa was supported by Swiss National Science Foundation via the Scientific Exchanges grants (proposal MENDEL). It is also important to highlight the circumstances in which the paper was prepared. The authors jointly worked to prepare results during 2021 and 2022, when NO visited Ukraine as a Visiting Professor. She has to run away from Kyiv early morning February 24th, 2022, when Russian terrorists started bombing Ukraine. NO journey to the western Ukrainian border with Poland took 4 days with sleepless nights by bus, but by February 28th, 2022 NO was able to safely arrive in Poland and shortly depart back home to the US. However, two of her colleagues, ML and MB remained in Ukraine and decided to continue working on the paper using Zoom calls and email exchanges. In March 2022, loud air ride siren could be heard during Zoom calls in Kyiv along with sounds of the explosions and nearby artillery. Nevertheless the paper was almost finished by the end of March 2022 and now it is ready to be presented to the attention of the scientific community.

Disclosure statement

No potential conflict of interest was reported by the author(s).