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Antiferroelectric materials are proposed as a potential solution to achieve multi-state memories, but the fundamental physical mechanism underlying the memory effect still needs to be clarified. Here, we study the memory effect in a typical antiferroelectric ceramic of Pb0.99Nb0.02[(Zr0.6Sn0.4)0.95Ti0.05]0.98O3 by systematically analyzing various hysteresis loops of polarization intensity and current density vs. electric field, where the kinetic behaviors are concerned about for the first time. The parallel pre-poling electric field reduces the critical electric field of antiferroelectric-ferroelectric phase transition, while the antiparallel field increases it. The memory behavior is significantly enhanced with the increasing of pre-poling time, but exhibits a remarkable weakening with the relaxation time increasing. It is a combined effect of electric-field-induced preferentially oriented antiferroelectric domains and internal bias electric field. This work not only improves comprehending in memory effect in antiferroelectric materials, but also enlightens the deeper understanding of other physical properties related to field-induced phase transitions.

The phase composition and their evolution in ferroelectrics are very complex near the morphotropic phase boundary (MPB), especially under multiple fields of electric field and temperature, which results in versatile behaviors of electrocaloric effect (ECE). This paper systematically studied the phase transitions and associated ECEs in the 〈001〉, 〈011〉 and 〈111〉 oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-30PT) single crystals with the chemical composition in the MPB area. Based on the dielectric and polarization responses under multi-fields, the refined electric field-temperature phase diagrams are established, wherein the ECE properties are closely related to the electric-field-induced phase transitions and exhibit a complex evolution across positive and negative values. The negative ECE originates from the transition from a monoclinic phase to a tetragonal or orthogonal phase under the noncollinear electric field, so it only appears in the 〈001〉 or 〈011〉 oriented crystals. Conversely, the transition from the tetragonal phase to the rhombohedral or orthogonal phase in the 〈111〉 or 〈011〉 oriented crystals induces a positive ECE peak with ∆Tmax = 0.40 K (@10 kV/cm). Just above Tm, the positive ECE reaches ∆Tmax = 0.61 K, 0.63 K and 0.68 K in the 〈001〉, 〈011〉 and 〈111〉 oriented crystals, respectively. In addition, there is an abnormal net endothermic phenomenon around the monoclinic-tetragonal or monoclinic-orthogonal phase boundaries due to the electric-field-induced irreversible transition.

The electrocaloric effect (ECE) of intrinsic-acceptor-doped ferroelectric system (1-x)Ba(Ti0.9Ce0.1)O3-x(Ba0.7Ca0.3)TiO3 (x = 0.3,0.5) has been studied by indirect and direct approaches. It was found that the indirect approach based on Maxwell equation is not appropriate for measuring the ECE of this acceptor-doped system. More importantly, a relatively large electrocaloric response is obtained at temperatures far below TC (maximum difference ~75 °C), which can reach 75%~90% of the maximum electrocaloric effect near TC. The unique characteristics of this acceptor-doped system have been explained by the existence of orientable defect dipoles. Our work could stimulate the design of temperature-stable electrocaloric effect through acceptor-doping.

Relaxor ferroelectrics, with polar nanoregions (PNRs), are good candidates for electrocaloric (EC) refrigeration. This study investigates the EC performance of the Pb1−1.5x La x Zr0.8Ti0.2O3 relaxor ferroelectric ceramics by the direct measurement using a modified differential scanning calorimeter. All the ceramics exhibit pure perovskite phase with a dense microstructure. The results indicate that the increasing La substitution strengthens the relaxor behaviour, promotes the transition from non-ergodic to ergodic state, and enhances the thermal stability of EC property (instability η

Electrocaloric effect (ECE) in ferroelectric (FE)/antiferroelectric (AFE) materials offers a promising high-efficient and zero-emission solid-state cooling technology, whose materials design is usually focused on the morphotropic phase boundary (MPB) between two FE phases. This work constructs an MPB between an orthorhombic AFE and a rhombohedral FE phase in Pb

Relaxor ferroelectrics continue to attract great attention for applications, including electrocaloric refrigeration, but the commonly used, indirect method of electrocaloric characterization based on the Maxwell relation often leads to artifacts. This analysis of long- and short-range ferroelectric order and the electrocaloric effect in Pb${}_{0.91}$La${}_{0.06}$Zr${}_{0.8}$Ti${}_{0.2}$O${}_{3}$ uses both direct and indirect characterizations, to clarify the applicability of the Maxwell relation to the physics of the relaxor, and the origin of discrepancies. It also suggests how to design relaxors with large electrocaloric effect by exploiting the transitions between polar nanoregions.

As an emerging solid-state refrigeration technology with zero-emission and high energy conversion efficiency, there is a compelling need for ferroelectric materials with giant electrocaloric effects (ECEs) at room temperature suitable for refrigeration applications. The complex perovskite antiferroelectric (AFE), PbMg0.5W0.5O3, containing non-equivalent B-site ions with a symmetric giant positive and negative ECE near room temperature is presented. At the Curie temperature of 36 °C, the first-order AFE–paraelectric phase transition gives rise to a large enthalpy change of 3.92 J g−1, more than four times that of BaTiO3. This leads to a significant ECE under the influence of an electric field. The direct electrocaloric characterization shows that the adiabatic temperature change, ΔT, exhibits symmetric peaks with a giant positive maximum of 1.79 K (ΔS = 1.68 J kg−1 K−1) at 36 °C and a negative maximum of −2.02 K (ΔS = −1.93 J kg−1 K−1) at 34 °C. The ultrahigh magnitude of ΔT near room temperature makes PbMg0.5W0.5O3 a superior electrocaloric material far beyond traditional PbZrO3-based AFEs. The coexistence of symmetric giant positive and negative ΔT to further improve cooling efficiency is expected. In addition, the good reversibility and negligible leakage current should pave the way for practical applications.

In this work, we develop a two-step sintering technology special for porous ceramics to resolve the contradiction between porosity and mechanical strength. It contains a first long-time sintering at the relatively low temperature (T1) and a second fast sintering at higher temperature (T2). Porous ceramics of aluminum titanate-strontium feldspar-mullite (ASM) ternary composite were prepared by this method, and exhibit both high porosity and high mechanical strength. The effects of T1 and T2 on the phase composition, microstructure, porosity, pore size distribution, mechanical strength and thermal expansion coefficient (TEC) of ASM porous ceramics are systematically studied. The sample sintered at T1 = 1400 °C & T2 = 1500 °C shows optimum performance: the porosity, bulk density, and mean pore diameter (D50) are 63.48%, 1.20 g/cm3 and 15.94 μm, respectively; while the flexural strength reaches 9.22 MPa and the TEC is 2.9 × 10−6/K. The two-step sintering technology provides a powerful tool to develop porous ceramics with excellent comprehensive properties.

The size of roots and their physiological activity during the grain-filling stage affect water and nutrient uptake, and grain yield (GY) in maize (Zea mays L.). The aim of this study was to determine the effects of different N levels on postanthesis root senescence in field-grown maize. Three N levels (0, 120, 240 kg N ha–¹) was applied to field-grown maize, and the length and weight of roots in the 0- to 40-cm soil layer, nitrogenous compounds in xylem sap, N uptake, dry matter (DM), N accumulation, and GY were analyzed. Shoot N accumulation, but not grain yield, was higher in the N240 treatment than in the N120 treatment. At the silking stage, the root length was longest in the N0 treatment and shortest in the N240 treatment. This was because of the high root/shoot (R/S) and root C/N ratios in N0. Total root length decreased throughout the grain-filling period, mainly because of the reduced length of early developed nodal roots. The root length decreased by 27% in the N0 treatment, to a smaller extent compared to that in N120 (52%) and N240 (51%). The amounts of NO₃⁻–N, NH₄⁺–N and amino acid-N in the xylem sap were highest in the N240 treatment during the entire grain-filling stage, suggesting that a high N supply increased root N-uptake activity. Based on these results, we conclude that high root N-uptake activity, not delayed root senescence, resulted in the large accumulation of N in the shoot under excess N.