Fig. 4: Atomic level microstructure and polarization configuration of x = 0.10.

a HAADF-STEM atomic image along the <100> _C direction. Inset is a schematic for the relative position of A/B sites in perovskite structure. b Intensity mapping of A-sites. Regions with significant contrast fluctuations are marked with yellow circles, indicating possible element substitution (Ca/Sr → Na) at these sites. c Intensity mapping of B-sites. Regions with significant contrast fluctuations are marked with yellow circles, indicating possible element substitution (Ti/Ta/Hf/Zr/Sn → Nb) at these sites. d Lattice spacing mapping for A-site species, characterizing local lattice distortions associated with A-A bonds caused by doping. e Lattice spacing mapping for B-site species, characterizing local lattice distortions associated with B-B bonds caused by doping. f Atom displacement mapping with monochromatic arrows on HAADF-STEM image background. g Extracted atomic displacement mapping with T₁ and T₂ polar nano regions (PNRs) indicated by blue and orange areas, respectively. Inset is a schematic of the polarization directions in the crystal structural coordinate system of x = 0.10. h Statistical atomic displacement distribution map for all polar vectors shown in (g). i Spatial distribution of relative angles of PNR directions. The values in the scale bars of (b and c) are the ratio of intensity of a specific site with respect to the statistical average intensity. The values in the scale bars of (d and e) are the ratio of the bond length of a specific bond with respect to the statistical average bond length. The spatial scale of (b–g) and (i) is the same as marked in (a).