Deformation of NaCoF.sub.3 perovskite and post-perovskite up to 30 GPa and 1013 K: implications for plastic deformation and transformation mechanism

• Published in: European journal of mineralogy (Stuttgart) Vol. 33; no. 5; p. 591
• Main Authors: Gay, Jeffrey P, Miyagi, Lowell, Couper, Samantha, Langrand, Christopher, Dobson, David P, Liermann, Hanns-Peter, Merkel, Sébastien
• Format: Journal Article
• Language: English
• Published: Copernicus GmbH 30.09.2021
• Subjects: Crystals; Earth; Mantle; Mechanical properties; Perovskite; Structure; Testing
• ISSN: 0935-1221

Texture, plastic deformation, and phase transformation mechanisms in perovskite and post-perovskite are of general interest for our understanding of the Earth's mantle. Here, the perovskite analogue NaCoF.sub.3 is deformed in a resistive-heated diamond anvil cell (DAC) up to 30 GPa and 1013 K. The in situ state of the sample, including crystal structure, stress, and texture, is monitored using X-ray diffraction. A phase transformation from a perovskite to a post-perovskite structure is observed between 20.1 and 26.1 GPa. Normalized stress drops by a factor of 3 during transformation as a result of transient weakening during the transformation. The perovskite phase initially develops a texture with a maximum at 100 and a strong 010 minimum in the inverse pole figure of the compression direction. Additionally, a secondary weaker 001 maximum is observed later during compression. Texture simulations indicate that the initial deformation of perovskite requires slip along (100) planes with significant contributions of {110} twins. Following the phase transition to post-perovskite, we observe a 010 maximum, which later evolves with compression. The transformation follows orientation relationships previously suggested where the c axis is preserved between phases and hh0 vectors in reciprocal space of post-perovskite are parallel to [010] in perovskite, which indicates a martensitic-like transition mechanism. A comparison between past experiments on bridgmanite and current results indicates that NaCoF.sub.3 is a good analogue to understand the development of microstructures within the Earth's mantle.