Fig. 1: In-situ observation of ferroelastic domain motion in BAI-N2 single-crystalline layered perovskites by polarized optical microscope.

a–f are in-situ polarized optical microscope images of the domain wall movement under applied stress in BAI-N2 crystals. The purple arrow indicates the bending sequence. The inset images show the bending states of the BAI-N2 single crystals and the red triangle represents the imaging direction. The red and black arrows in (a) indicate the analyzer and polarizer orientation, respectively. The dark line in the center is a surface scratch, which is chosen as a location marker.