TEM study of incommensurate superstructure in Pb_1−0.5xNb_x((Zr_0.52Sn_0.48)_0.955Ti_0.045)_1−xO₃ ceramics with 0–1 switching characteristic strain and high energy storage density

Pb_1−0.5xNb_x((Zr_0.52Sn_0.48)_0.955Ti_0.045)_1−xO₃(PNZST-100x (x = 0.01, 0.02, 0.03, 0.04)) antiferroelectric (AFE) ceramics were prepared using a solid-state method. X-ray diffraction analysis indicates a structural evolution from the tetragonal phase to the pseudocubic phase. When x = 0.02, the ceramic exhibits an enhanced energy storage density of 1.37 J/cm³, and a strain, with 0–1 switching characteristics, of 0.22%. Selected-area electron diffraction (SAED), high-resolution transmission electron microscopy imaging, and in-situ TEM analyses indicate that there are two kinds of superlattice reflections, including the 1/2(hkl) superlattice reflection (h, k, and l: all odd) and 1/6.67(a* + b*) one-dimensional incommensurate superlattice reflections. The origin of the 1/2(hkl) superlattice reflection was the tilting of a^-a^-a^- oxygen octahedra. Therefore, the 1/2(hkl) reflections were no longer superlattice reflections, but fundamental reflections in the trigonal system; hence, the reciprocal vector was re-expressed as \(H\, = \,ha^{*} \, + \,kb^{*} \, + \,lc^{*} \, \pm \,1/6.67\left( {a^{*} \, + \,b^{*} } \right),\) where h, k, and l are integers and (− h + k + l) = 3n. The incommensurate structure of the PNZST-2 ceramic originated from the displacement of Pb²⁺.