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Environmentally friendly lead-free dielectric ceramics have attracted wide attention because of their outstanding power density, rapid charge/dischargerate, and superior stability. Nevertheless, as a hot material in dielectric ceramic capacitors, the energy storage performance of Na0.5Bi0.5TiO3-based ceramics has been not satisfactory because of their higher remnant polarization value and low dielectric breakdown strength, which is a problem that must be urgently overcome. In this work, the (1 - x) (0.6Na0.5Bi0.5TiO3 - 0.4Sr0.7Bi0.2TiO3) - xBa(Mg1/3Ta2/3)O3 (BNST-xBMT) systems were designed based on a dual optimization strategy of domain and bandgap to solve the above problems. As a result, a record-breaking ultrahigh energy density and excellent efficiency (Wrec = 8.58 J/cm3, η = 93.5%) were obtained simultaneously under 565 kV/cm for the BNST-0.08BMT ceramic. The introduction of Sr0.7Bi0.2TiO3 induces the formation of nanodomains in BNT-based ceramics, leading to slim P-E curves, and the further modification of Mg/Ta reduces the grain sizes and increases the bandgap width, resulting in significant enhancement of the dielectric breakdown strength. Moreover, excellent stability and superior discharge performance (Wd = 4.7 J/cm3, E = 320 kV/cm) in the BNST-0.08BMT ceramic were also achieved. The results suggest that the BNST-0.08BMT ceramic shows potential applicability for dielectric energy storage ceramics. Simultaneously, the composition-design concept in the system provides a good reference for the further development of ceramic dielectric capacitors.

Soil salinity and alkalinity can inhibit crop growth and reduce yield, and this has become a global environmental concern. Combined changes in nitrogen (N) application and hill density can improve rice yields in sodic saline–alkaline paddy fields and protect the environment. We investigated the interactive effects of N application rate and hill density on rice yield and N accumulation, translocation and utilization in two field experiments during 2018 and 2019 in sodic saline–alkaline paddy fields. Five N application rates (0 (control), 90, 120, 150, and 180 kg N ha–1 (N0–N4), respectively) and three hill densities (achieved by altering the distance between hills, in rows spaced 30 cm apart: 16.5 cm (D1), 13.3 cm (D2) and 10 cm (D3)) were utilized in a split-plot design with three replicates. Nitrogen application rate and hill density significantly affected grain yield. The mathematical model of quadratic saturated D-optimal design showed that with an N application rate in the range of 0–180 kg N ha–1, the highest yield was obtained at 142.61 kg N ha–1 which matched with a planting density of 33.3×104 ha–1. Higher grain yield was mainly attributed to the increase in panicles m–2. Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants and showed a highly significant positive correlation with grain yield at maturity. From full heading to maturity, the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3. This is one of the reasons why the yield of N4 treatment is lower than that of the N3 treatment. Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha–1) were 81.68 and 106.07% higher in 2018 and 2019, respectively, than those in the control. The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density, whereas N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density. Agronomic N-use efficiency decreased with an increase in N application rate, whereas hill density did not significantly affect it. Nitrogen productivity of dry matter and grain, and agronomic N-use efficiency, were negatively correlated with grain yield. Thus, rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation. Our study provides novel evidence regarding optimal N application rates and hill densities for sodic saline–alkaline rice paddies.

A depolarized electric field (Edp) of ferroelectrics to boost the carrier separation and migration rate is critical to promote the field of visible light photocatalytic hydrogen evolution (PHE). Here, the PHE performance of high-field poled semiconducting (1 − x)KNbO3–xBa(Ni1/2Nb1/2)O3−δ (abbreviated as (1 − x)KN-xBNN, x = 0, 0.02, 0.05, 0.10, and 0.20) ferroelectric ceramics were systematically studied under full spectrum (λ > 320 nm) and visible light (λ > 420 nm), respectively. Benefiting from their narrow bandgap and sub-bandgap, all the Ba, Ni-modified KN ceramic powders exhibited a PHE response under visible light irradiation. Notably, the visible light PHE rate of the high-field poled 0.95KN–0.05BNN ceramic powder can be promoted to 415.16 μmol g−1 h−1, which is 17.8-fold higher than that of the unpoled sample (23.26 μmol g−1 h−1). The boosting PHE rate in poled samples can be attributed to the high-field polarization of the material, which can significantly affect the lattice structure and cause an ordered ferroelectric-domain structure to form a depolarized electric field (Edp). EPR spectroscopy indicated that the poled 0.95KN–0.05BNN sample exhibited a superior catalytic activity of ˙OH evolution compared with its unpoled counterpart, suggesting the dependence of high photocatalytic performance on the unique field-induced polarization structure by an outer electric field. Moreover, a higher photo-excited transient photocurrent in the poled 0.95KN–0.05BNN specimen further proved the positive effect of Edp on the photovoltaic response. The formation of Edp in the semiconducting (1 − x)KN–xBNN ferroelectric favors the separation and transportation of photogenerated carriers. Thus, the synergistic effect of narrow bandgap and high-field polarization ability is the key to enhance the visible light photocatalysis of semiconducting ferroelectrics. Boosting the visible light photoelectrochemical catalytic activity of semiconducting (1 − x)KN–xBNN ferroelectrics through high-field polarization may provide a useful strategy to design new ferroelectric-based semiconductor materials.

Environmentally friendly lead-free dielectric ceramics have attracted wide attention because of their outstanding power density, rapid charge/dischargerate, and superior stability. Nevertheless, as a hot material in dielectric ceramic capacitors, the energy storage performance of Na

Novel perovskite ferroelectric (1-x)KNbO3-xBi(Ni1/2Ti1/2)O3 nanofibers were synthesized by electrospinning for the first time. The synthesized 0.99KNbO3-0.01Bi(Ni1/2Ti1/2)O3 nanofibers displayed the optimal photocatalytic activity with a hydrogen production rate of 0.57 μmol·h−1 for 20 mg under visible light radiation. By first principles calculations, a midgap of Ni 3d was formed between the O 2p states at the valence band maximum and the Nb 4d states at the conduction band minimum due to the addition of Bi(Ni1/2Ti1/2)O3, which may be the principal reason for the visible light response in this work. In addition, the hydrogen production rate of polarized 0.99KNbO3-0.01Bi(Ni1/2Ti1/2)O3 nanofibers was twice as high as that of unpolarization under visible light irradiation, indicating that the internal dipole field can accelerate the separation of photogenerated electron-hole pairs. This may provide a new viewpoint for improving the visible light response of perovskite-oxide ferroelectrics.

The new (1-x) Bi0·5Na0·5TiO3-xCoTiO3-δ ferroelectric semiconductor ceramics were prepared successfully by the solid-state method. The single perovskite structures and long-range polarity order of the (1-x) Bi0·5Na0·5TiO3-xCoTiO3-δ semiconductor ceramics were observed by X-ray diffraction (XRD) and Raman spectra, respectively. The typical relaxation behavior was founded in all the ceramics. The perfect ferroelectric loops and outstanding optical properties were achieved in the (1-x) Bi0·5Na0·5TiO3-xCoTiO3-δ ceramics. A very small optical bandgap (Eg = 1.44 eV) was obtained in the 0.94Bi0·5Na0·5TiO3-0.06CoTiO3-δ ceramic, which is approximately 55% lower than that of pure BNT (Eg = 3.2 eV). The Jsc and Voc of poled 0.94Bi0·5Na0·5 [Ti4+0.71, Ti3+0.29]O2.71-0.06Co [Ti4+0.71, Ti3+0.29]O2.71 ceramic can reach ~ 1.00 nA/cm2 and 0.13 V, respectively. The activation energies of the grains and grain boundaries were calculated to be 0.48 and 0.52 eV, respectively. These results show that the Co substation BNT ceramics highlight a promising candidate for multi-functional photoelectric applications.