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Materials with electrocaloric effect (ECE) and/or thermal switching ratio λ are desirable for developing various heat management devices, but developing high-performance candidates, especially those that simultaneously possess large near room-temperature ECE and λ is actually absent. The Zr-rich PbZr1−xTixO3 (PZT) displays a composition-induced antiferroelectric-ferroelectric (AFE-FE) phase boundary, where an unusual negative ECE is expected. Meanwhile, the electric field-sensitive dipole orientation during the AFE-FE phase transition can be employed to modulate λ. In this work, the Zr-rich PZT with coexisting AFE and FE phases was developed and the AFE-FE phase transition temperature is tuned toward room temperature by changing the Ti content to achieve large negative ECE and λ. A large adiabatic temperature change ΔT of −3.3 K accompanied by a giant λ of 1.84 near 60 °C is captured in optimal PbZr0.95Ti0.05O3 ceramics, demonstrating a prominent application prospect in solid-state refrigeration. [ABSTRACT FROM AUTHOR]

Rare-earth titanate pyrochlores have attracted significant attention for their unique magnetic frustration; however, research on the origin of low-temperature dielectric dispersion and the relationship between dielectric properties and structure lags far behind. Here, by systematically investigating the dielectric properties of representative rare-earth titanates R2Ti2O7 (R = La, Nd, Sm, Er, Yb, and Lu), we demonstrate that R2Ti2O7 with a cubic pyrochlore structure exhibits low-temperature dielectric dispersion behavior, while the other compounds with a monoclinic perovskite-like layered structure possess no dispersion behavior but excellent temperature-stable dielectric property. The dielectric dispersion in cubic pyrochlores arises from the structural distortion. Furthermore, the existence of structural distortion is affirmed by the anomalous phonon softening of A1g Raman mode around the dielectric dispersion temperature, and the origin of the structural distortion is attributed to anharmonic phonon–phonon interactions induced by intrinsic vacant oxygen at Wyckoff 8a sites. In addition, with increasing ionic radius from R = Lu to Sm, the increased lattice parameter leads to varied bond length and bond angle of Ti-O(1)-Ti, which strengthens the local lattice distortion of TiO(1)6 octahedra and thus enhances diffusion degree of dielectric dispersion. On the other hand, the absence of intrinsic vacant oxygen site hardly gives rise to the local structural distortion and thus no dielectric dispersion in monoclinic R2Ti2O7. Our work not only clarifies the mechanism of dielectric dispersion but also gives a comprehensive perspective on the structure–property relationship of rare-earth titanates R2Ti2O7, and thus lays a solid foundation for further work on related materials. [ABSTRACT FROM AUTHOR]

As the two typical basic binary solid solutions of the relaxor-PbTiO3 family, Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) has been widely investigated, whereas Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) has not. Here, 1.5 mol% Sm-doped (1 − x)Pb(Ni1/3Nb2/3)O3–xPbTiO3, (1 − x)PNN–xPT:0.015Sm with x = 0.33–0.39, ceramics have been prepared and the chemical composition-induced evolution of crystal structure, domain, and electrical properties investigated systematically. With increasing PT content, evolution of the rhombohedral–tetragonal structure was observed. A rhombohedral–tetragonal morphotropic phase boundary occurred around x = 0.36–0.37, which showed a peak piezoelectric property with piezoelectric constant d33 = 531 pC N−1 and planar electromechanical coupling factor kp = 0.37 at room temperature. At the same time, the x = 0.36 composition showed improved ferroelectric behavior with remanent polarization Pr = 13.4 μC cm−2 and coercive field Ec = 3.2 kV cm−1. Interestingly, different from its PMN-PT counterpart, there is no temperature-driven phase transition between room temperature and the Curie temperature for (1 − x)PNN–xPT:0.015Sm. These parameters indicated that the PNN-PT system is worthy of more attention and is a promising platform for further development of high-performance piezo/ferroelectric materials. [ABSTRACT FROM AUTHOR]

The observation of the anomalous Hall effect (AHE) in 5d perovskite oxides has been challenging due to their lack or weak ferromagnetic order, which is necessary for breaking time-reversal symmetry. Here, we present compelling evidence of ferromagnetism and consequent AHE in a series of carefully designed and fabricated 5d/5d SrTaO3/SrIrO3 (STO/SIO) superlattices. The coexistence of Ta5+ and Ta4+ chemical states induces ferromagnetism in the STO layer, while the interfacial magnetic proximity effect further enhances it in the SIO layer, resulting in both ferromagnetism and AHE within the STO/SIO superlattice. Additionally, the strong spin–orbit coupling between Ta and Ir elements positively contributes to enhancing the AHE. This work offers an alternative approach for designing artificial materials with AHE and holds potential for advancing spintronics. [ABSTRACT FROM AUTHOR]

Unusual substitutional and interstitial solid solutions were observed in (1−x)Ba(Zr0.35Ti0.65)O3-xZnO thin films, where one Zn2+ cation substituted one B-site Zr4+/Ti4+ site and two Zn2+ cations substituted one A-site Ba2+ site simultaneously. Such a hybrid solid solution with an appropriate ZnO content remarkably increases both the electric breakdown strength (Eb) by widening the bandgap and the energy storage efficiency (η) by suppressing the hysteresis of the ferroelectric loop. As a result, the films with x = 0.2 show superior energy storage performance with a recoverable energy storage density (Wrec) of 130.3 J/cm3 and η of 89.1%. This work confirms the feasibility of forming an unconventional hybrid solid solution, which may shed light on further work on perovskite oxides with improved ferroic functionalities. [ABSTRACT FROM AUTHOR]