Plastic deformation of CaTiO3 perovskite under extreme loading

Abstract

Perovskites are important functional materials in modern technology, with numerous applications in optoelectronics, such as solar cells and LEDs, lasers, and other fields. Importantly, the lower Earth mantle is predominantly composed of perovskite. (Mg, Fe)SiO₃ and CaSiO₃, two of the most abundant minerals in the Earth's mantle, are not amenable to being investigated at ambient conditions because they are not stable. CaTiO₃ serves as an excellent analogue. Thus, high-energy laser shock compression was employed to investigate the deformation mechanisms and mechanical behavior of [010] oriented CaTiO₃ under extreme pressure and temperature conditions comparable to those in the mantle, albeit at significantly higher strain rates. The shear stress generated by the 70 GPa shock stress was equal to approximately 20 GPa, assuming elasticity. This is significantly higher than the Peierls-Nabarro stress required to move dislocations, around 10 GPa. In agreement with this, transmission electron microscopy revealed the generation of profuse perpendicular dislocations in [110](001) and [$\overline{1}$10](001) slip systems. The dislocation density ranged from 15×10¹² m⁻² to 2×10¹² m⁻² within 12 µm from the shocked surface. Additionally, antiphase domain boundaries along [010] and [100] were observed under the high-pressure shock conditions. CaTiO₃ deforms mainly through dislocation motion due to its positive Clapeyron slope and high atomic packing factor. This study sheds light upon the plastic deformation of (Mg, Fe)SiO₃ and CaSiO₃, which comprise most of the lower earth mantle.