Piezoelectric and ferroelectric ceramics with a high Curie temperature (Tc) have attracted much attention owing to their applications in severe environments. In this work, phase structure and dielectric, ferroelectric, and piezoelectric properties of (0.975 − x)BiScO3-xPbTiO3-0.025Pb(Cd1/3Nb2/3)O3 (BS-xPT-PCN) ceramics (x = 0.58–0.64) were studied. A composition-induced structural transformation occurs from the rhombohedral to tetragonal phase through an intermediate monoclinic phase with the increasing PT concentration. The relationship between the structure and electrical properties of the system was discussed. The BS-xPT-PCN system near the morphotropic phase boundary (MPB) (x = 0.62) exhibits excellent piezoelectric and ferroelectric performances with d33 = 508 pC/N, kp = 56%, and Pr = 40 μC/cm2. The high-temperature piezoelectricity of the sample with MPB (x = 0.62) was characterized by an in situ XRD. The excellent thermal stability of the crystal structure and the piezoelectric property indicate that the BS-xPT-PCN system is a promising candidate for high-temperature piezoelectric applications.

The 0.65Bi(Mg1/2Ti1/2)O3‐0.35PbTiO3 (0.65BMT‐0.35PT) ceramic, nearby morphotropic phase boundary (MPB), between tetragonal and rhombohedral was prepared. Dielectric permittivity dependence of temperature exhibits a re‐entrance dipole glass‐like behavior near room temperature. The behavior was described by the Vogel‐Fulcher law and the new glass model. Furthermore, a phenomenological statistical model was employed to determine the distribution of clusters dependence of temperature. The lattice dynamics of the 0.65BMT‐0.35PT ceramic was estimated by Raman spectroscopy from 298‐723 K. A disruption of ferroelectric long‐range order and an occurrence of local lattice distortion were revealed. The relaxor‐ferroelectric (r‐FE) nature of the 0.65BMT‐0.35PT was characterized by polarization‐electric field P(E). A close relation between the distribution of clusters and ferroelectric properties was established.

The existence of polar nanoregions (PNRs) is the most important characteristic of ferroelectric relaxors; however, the size determination and the dynamic of PNRs remain uncertain. Herein, it is revealed that a re‐entrant relaxor behavior and ferroelectric–paraelectric transition coexist in complex perovskite oxide 0.6Bi(Mg1/2Ti1/2)O3‐0.4PbTiO3. Two dielectric anomalies, 1) the low‐temperature re‐entrant relaxor transition and 2) the high‐temperature diffuse phase transition (DPT), are described by the phenomenological statistical model. The sizes of the two kinds of PNRs corresponding to two ferroelectric states were obtained. The dynamics of PNRs are analyzed using isothermal electrical modulus, which shows three critical temperatures associated with the DPT, the formation, and freezing of PNRs, respectively. The temperature evolution of the PNRs evolution depends on the stoichiometry of bismuth. The results provide new insights into the dynamic behavior of PNRs and the modification way of re‐entrant relaxor behavior.

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Ta2O5-doped 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 [(1 − x)(0.94BNT-0.06BT)-xTa (x = 0.00-0.02)] ceramics were prepared by a solid-state reaction technique. The single perovskite structure with space group R3c of the ceramics was identified by X-ray diffraction (XRD). Raman spectroscopy revealed the evolution of the local structure with Ta2O5 concentration. The temperature dependence of dielectric permittivity of the ceramics were deconvoluted by three Gaussian distribution functions which suggests that three dielectric anomalies exist in this system. The low-temperature dielectric anomaly exhibits a typical relaxor behavior with strong frequency dispersion (reentrant relaxor behavior). The activation energy derived from the V-F law is 0.298 eV, 0.338 eV, 0.412 eV and 0.449 eV, for x = 0.00, 0.005, 0.01 and 0.02, respectively. The mid-temperature and high-temperature anomalies are attributed to two structure phase transitions. The increase of the activation energies suggests that the coupling between polar clusters or polar nanoregions (PNRs) becomes weaker. The origin of the interaction between PNRs and phase transition behavior has been proposed according to the average structure, local structure and defect compensation mechanism of the system.