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Fig. 63: Maps of the integrated intensity (left panels) and lattice tilt (right panels) of the nanoplatelet at selected temperatures along the heating cycles. The maps are stacked from top to
bottom following the chronological order.
PRINCIPAL PUBLICATION AND AUTHORS
In situ imaging of temperature-dependent fast and reversible nanoscale domain switching in a single-crystal perovskite, L.A.B. Marçal (a,b), D. Dzhigaev (a), Z. Zhang (a), E. Sanders (c), A. Rothman (c), E. Zatterin (d), E. Bellec (d), T. Schulli (d), A. Mikkelsen (a), E. Joselevich (c), J. Wallentin (a), Phys. Rev. Mat. 6, 054408 (2022); https:/doi.org/10.1103/PhysRevMaterials.6.054408 (a) Synchrotron Radiation Research and NanoLund, Lund University (Sweden) (b) MAX IV Laboratory, Lund University (Sweden) (c) Department of Materials and Interfaces, Weizmann Institute of Science (Israel) (d) ESRF
 W. Zhang et al., Nat. Energy 1(6), 16048 (2016).  L.A.B. Marçal et al., ACS Nano 14, 15973 (2020).  L.A.B. Marçal et al., Phys. Rev. Mat. 5, L063001 (2021).
Fig. 62: a) Schematic representation of the FFDXM experimental setup.
The nanoplatelet was rotated to the Bragg angle θ, and the X-ray detector
was positioned at 2θ. The bright areas are domains with both lattice
tilts aligned by the rotation motor as well as lattice spacing within the 2θ
condition selected by the lenses. The lenses create a 65x magnified image
of the bright parts of the nanoplatelet on the detector. b) Projections at a
specific θ of the nanoplatelet acquired at temperatures ranging from 20°C
to 70°C during temperature increase. c) Images near 75.7°C, evidencing
a sudden change in the domain orientation pattern in the central part.
d) Images near 83.3°C, showing another sudden change in the left part
of the nanoplatelet.
seen at different temperatures close to the nominal orthorhombic to tetragonal critical point (Figures 62c and 62d). Significant differences could be noted in the domains from 75.6°C to 75.7°C (Figure 62c) as well as from 83.2°C to 83.3°C (Figure 62d), even more prominent than changes seen along 10°C in Figure 62b. This shows that the domains change at different temperatures, despite being part of the same single crystal.
The reversibility of the dynamics was also investigated by rotating the nanoplatelet along the rocking angle at 20°C and 80°C in multiple heating cycles. MHPs are known for being very sensitive to radiation, degrading very fast under an intense X-ray beam. However, FFDXM is a low-dose technique when compared to nano-XRD, which allowed multiple heating cycle measurements. For each angle, different domains were aligned in the Bragg condition and consequently became visible along the nanostructure. Full rocking curve images show consistent similarities in all 20°C as well as all 80°C maps (Figure 63). This work shows that the single crystal reversibly and deterministically switches between a low- temperature and a high-temperature pattern.