Ba(Ti_0.25Zr_0.25Hf_0.25Sn_0.25)O₃ high-entropy ceramics were prepared by a standard solid state reaction process, and the dielectric and ferroelectric characteristics were investigated together with the structures. Both X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis demonstrated a single-phase perovskite structure in the present ceramics. A broad dielectric peak with strong frequency dispersion feature was determined, which indicated the typical relaxor nature originating from the nanoscale ferroelectric domain structures. These resulted from the structural distortion and chemical disorder due to high-entropy, where the long-range order of ferroelectric domains was destroyed. The homogeneous microstructure led to the reduced leakage current density and significantly improved dielectric strength, which was desired for the practical applications. Compared with the similar systems of Ba(TiZr)O₃ & Ba(TiSn)O₃, the present high-entropy ceramics indicated better relaxor ferroelectric characteristics.

Ordered domain engineering has been further developed for modifying and improving physical properties in complex perovskite ceramics. In the present work, Ba(Ni_1/3Nb_2/3)O₃ ceramic is taken as a typical example for ordered domain engineering, in which the sintering temperature lies above the order-disorder transition temperature. Though the well-ordered structure could not be obtained in as-sintered samples, high ordering degree could be achieved together with preferred ordered domain structures in Ba(Ni_1/3Nb_2/3)O₃ ceramics through long-time annealing, and subsequently the physical properties such as electrical resistivity, thermal conductivity, dielectric strength and energy storage density are significantly enhanced, where the ordering degree, ordered domain structure and ordered domain boundary play the critical rules. The present work provides an effective approach for developing complex perovskite dielectric ceramics with superior physical properties.