Unusual devisable high-performance perovskite materials obtained by engineering in twins, domains, and antiphase boundaries

With the widespread application, engineering of microstructures, domains, twins, and antiphase boundaries (APBs) is attracting significant attention. However, the origin of the domains, especially in the paraelectric phase, as well as the mechanism of variation in twins or domains and their relationship are still not clear. Generally, these structures are recognized as one of the key origins of intrinsic loss. Our studies, however, reveal that the formation of twins is closely related to the asymmetry of the crystal structure. With the introduction of a lattice blockage-trigonal NdAlO₃ phase, the increase in the symmetry of the CaTiO₃ tetragonal phase results in a transformation from the (110)-oriented twins to the (111)-oriented twins. Then, it forms a new ordered structure. With the help of peak-differentiation and imitation of the Raman spectra, the A-site in the perovskite structure is found to be a dominant factor in lattice energy and performance. By designing an A-site displacement, i.e., Sr²⁺ or Ba²⁺ substitution into Ca²⁺, we created a controllable structure of twins by symmetry regulation and APBs by introducing ferroelectric spontaneous polarization. Via selected area electron diffraction patterns (SAED) and variable temperature electric field piezoresponse force microscopy (PFM) images, we found that 180° and 90° domains could coexist in the grains of xCaTiO₃-(1 - x)NdAlO₃ ceramics. Interestingly, the 90° domains and twin boundaries (TB) play more important roles in the anisotropic resistance to the electron/hole transfer. Our studies prove that the defect engineering can realize a controllable enhanced dielectric performance by defect regulation within the host lattice. These may pave a possible way for the design of the microstructure of the defects to achieve better predictable performances of the materials.