SrTiO3(STO) is an important grain boundary layer capacitor material and has extensive applications in integrated and microwave circuits. In this work, SrTiO3 precursor powder was prepared using the solid-phase sintering method, and STO ceramic capacitors with a thickness of 0.2 mm were fabricated by the tape casting method. Effects of synthesis conditions, especially synthesis temperature and time, on the structure, morphology and electrical properties of STO were investigated through characterization methods such as XRD, SEM, TG-DSC, and dielectric property measurements. The relationship between the morphology and grain size of STO and its dielectric properties was also explored. The results indicate that 1250 ℃ and 1440 ℃ are the critical temperatures(beginning and complete formation) for preparing SrTiO3 through solid-state sintering of SrO and TiO2. When the temperature is below 1250 ℃, SrO and TiO2 remain in initial raw material powder states, and SrTiO3 cannot be synthetized. As the temperature exceeds 1250 ℃, the contact interface between SrO and TiO2 begins to react, and result in the formation of SrTiO3 through a solid-phase reaction. In addition, 1440 ℃, as the eutectic point between SrTiO3 and TiO2, is the optimal temperature for synthesizing SrTiO3 with mature grains and the best electrical performances. Moreover, the results show that with the increase of synthesis temperature and time, the grain size of STO first increases, and then decreases if further increasing synthesis temperatures and time. When the synthesis condition is 1440 ℃ × 2 h, the average size of STO grain reaches a maximum value of 1.76 μm and STO has the best dielectric properties with a dielectric constant of 25,000, a loss of 1.25

Nickel ferrite (NiFe 2 O 4 ) is an attractive pseudocapacitive electrode owing to its reversible Ni 2+ /Ni 3+ and Fe 2+ /Fe 3+ redox couples.

Magnetic-field-assisted synthesis provides an effective route for regulating the microstructure and defect chemistry of ferrite-based electrode materials. However, the coupled effect of magnetic-field-induced assembly and defect evolution on the pseudocapacitive behavior of nickel ferrite (NiFe2O4) remains insufficiently clarified. Herein, NiFe2O4 samples were prepared by a magnetic-field-assisted hydrothermal method, and their structural evolution, surface chemical states, and electrochemical kinetics were systematically investigated under different magnetic-field conditions. The applied magnetic field promoted the chain-like self-assembly of NiFe2O4 nanoparticles, resulting in a more continuous conductive network, improved pore connectivity, and enhanced electrolyte accessibility. Meanwhile, the magnetic field increased the concentration of oxygen vacancies, which facilitated OH- adsorption/activation and strengthened the contribution of fast surface Faradaic reactions. Benefiting from the synergistic regulation of chain-like architecture and defect-rich surfaces, the optimized NFO-3 electrode exhibited markedly improved specific capacitance at 1.0 A g−1 and maintained a capacitance retention of 95.18% after cycling. Even at a high current density of 10 A g−1, NFO-3 still delivered a cycling stability of 90.59%. These results demonstrate that magnetic-field-assisted hydrothermal synthesis is a feasible strategy for tailoring the assembly behavior and defect structure of ferrite oxides, providing a useful approach for designing high-performance ceramic electrode materials for pseudocapacitive energy storage.

In this study, based on the Gouy-Chapman-Stern double-layer model (GCSDLM), we systematically investigate the diffusion behavior of solution ions toward the electrode surface, the evolution of the diffuse layer potential under the magnetohydrodynamic (MHD) influence, and the resulting enhancement mechanism for the charge storage performance of Electric Double-Layer Capacitor (EDLC), using a combination of multi-physics simulations (COMSOL) and experimental validation. The results show that within a magnetic field range of 0-0.57 T, the current density of the EDLC follows the theoretically predicted B1/3 scaling law, with good agreement between experimental data and simulation results. The performance improvement stems from the MHD effect, whereby the magnetic field modulates the electrolyte microstructure and interfacial Zeta potential, thereby inducing helical ion motion, enhancing mass transfer, reducing the diffusion-layer thickness, and increasing the current density. Moreover, a high capacitance retention of 92% is maintained after 2000 cycles at 0.57 T. This study provides new insights and experimental support for the regulation of energy storage behavior in EDLC using magnetic fields.

The influence on the pseudocapacitance performance of nickel ferrate (NiFe2O4) using magnetic field orientation approach was investigated in this work. NiFe2O4 were synthesized by hydrothermal method, and the electrode materials with parallel (Para) and perpendicular (Perp) directions were obtained by aligning NiFe2O4 particles in an external magnetic field of 3000 Gs. The results demonstrate that magnetic field treatment significantly optimizes the microstructure of NiFe2O4. The vertically oriented sample exhibited the best performance, showing a 21.2% increase in the CV peak current and a specific capacitance of 325.64 F/g at 1 A/g-a 25.7% improvement over the non-oriented sample. Structural characterization revealed that the vertically oriented sample exhibited preferential alignment along (400) and (440) crystal planes, leading to optimized microstructure and charge transport pathways. Electrochemical impedance analysis revealed that the vertically oriented sample possessed the lowest charge transfer resistance (Rct) of 0.033 Omega and the highest ion diffusion coefficient of 6.77 & times; 10-8 cm2/ s, implying that the ordered arrangement of particles induced by the external magnetic field effectively promotes the carrier transport kinetics. Furthermore, the vertically oriented sample maintained 51.57% capacitance retention after 5000 cycles, representing a remarkable improvement of 14% compared to the non-oriented sample (37.5%). Our work demonstrates that the pseudocapacitive performance of NiFe2O4 can be considerably enhanced by magnetic field, and provide a new idea for making electrodes with a high performance.

Regulating electronic structure via a uniform magnetic field effectively optimizes catalytic performance, yet rationally utilizing external magnetic fields to tune catalyst structure, promote small-molecule oxidation, and clarify mechanisms remains a key challenge. Here, a 0.7 T magnetic field was introduced during Fe-Ni2P@NF electrochemical activation to construct a Ni & horbar;O & horbar;Fe heterogeneous oxygen bridge, boosting urea oxidation (UOR) and hydrogen evolution (HER). In situ Raman revealed the magnetic field-induced Ni & horbar;O & horbar;Fe formation on 0 T and 0.7 T Fe-Ni2P@NF surfaces-this structure is more stable than NiOOH and functions as an electron transfer channel from Fe to Ni. Infrared spectroscopy revealed synergistic dual-site behavior: Ni sites enhance urea adsorption, while Fe sites in the Ni & horbar;O & horbar;Fe bridge stabilize *OH species; electron donation from Fe to Ni through the oxygen bridge promotes Ni-2(+) oxidation to higher-valent states (Ni-3(+)/Ni-4(+)), activating Ni centers for UOR. DFT calculations supported this electronic modulation mechanism-Fe-mediated electron transfer upshifts the Ni d-band center, strengthening urea adsorption and lowering the *NH & horbar;O ->*N & horbar;O rate-determining step barrier. Notably, at 100 mA cm(-)(2), 0.7 T-Fe-Ni2P@NF powers the HER//UOR electrolyze at only 1.54 V, outperforming water electrolyzes (1.62 V).

This paper reports that flexible composite films containing BiFeO3 nanoparticles demonstrate substantial electrocaloric strength and adiabatic temperature change of 407 mK m MV-1 and 24.4 K for a 10 wt% solid content, respectively. These values significantly surpass previously reported data. We discovered that crystallite sizes exceeding 10 nm in the polar beta-phase are essential for amplifying the electrocaloric effect, allowing for easier domain motion at lower electric fields. Simulations based on Landau theory validate the electrocaloric effect in the BiFeO3/P(VDF-TrFE) composite film, predicting it can induce a 34 K adiabatic temperature change under 120 MV m-1. This finding offers a basis for selecting between high cooling performance and energy efficiency for practical applications. The research showcases a flexible composite film with potential practical applications in solid-state refrigeration technologies.

In this study, SrTi1-x(Ta1/2Li1/2)(x)O-3 ceramics were successfully synthesized via the solid-state reaction method. The sample with x = 0.5 % exhibits excellent dielectric properties, showing a colossal permittivity as high as 100,937 and a low dielectric loss of 0.047 at 1 kHz. Furthermore, the ceramic demonstrates excellent temperature stability over the range of -55 degrees C-200 degrees C, satisfying the criterion of (epsilon - epsilon(25 degrees C))/epsilon(25 degrees C) < +/- 15 %, and meeting the EIA X9R standard. X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and AC impedance spectroscopy analyses reveal that the co-doping strategy of Ta5+ and Li (+) not only enhances the flexibility of doping control but also introduces a greater variety of defect dipoles and defect dipole clusters, such as Ti-Ti(y)-V-O(& sdot;)-Ti-Ti(y), Ta-Ti-V-O(& sdot;& sdot;)-3Ti(Ti)(y), and Li-Ti(y)-V-O(& sdot;)-Ta-Ti(& sdot;). These defect dipoles and clusters exert a "pinning effect" on free charge carriers, restricting their long-range migration, enhancing local polarization, and reducing dielectric loss, thereby further optimizing the dielectric properties of the material.

In this study, SrTi1-xTaxO3 (x = 0 %, 0.1 %, 0.3 %, 0.5 %) ceramics were synthesized using the solid-state reaction method, and the effects of Ta5+ ions doping on the phase structure, microstructure, defect type, dielectric properties and AC impedance characteristics of ceramic samples were investigated. The results indicated that the SrTi1-xTaxO3 ceramics with x = 0.3 % demonstrated a colossal permittivity (11423 @ 1 kHz), low dielectric loss tangent (0.05 @ 1 kHz), as well as excellent temperature stability, which met the temperature stability requirements of the EIA X9R standard over a wide temperature range (-55 degrees C-200 degrees C, Delta epsilon/epsilon 25 degrees C <= +/- 15 %). XPS and AC impedance spectroscopy analyses revealed that the formation of defect dipoles and their clusters related to oxygen vacancies ((TiTi)-Ti-y-V & sdot;& sdot;O-(TiTi)-Ti-y and Ta & sdot;Ti-V & sdot;& sdot;O-3 (TiTi)-Ti-y) was the fundamental cause of the excellent dielectric performance of SrTi0.997Ta0.003O3 ceramics. This study makes a significant contribution to the exploration of SrTiO3-based colossal permittivity ceramics with excellent temperature stability through defect engineering.

Hydrothermal method was used to directly grow the anatase crystal of TiO2, followed by a detailed discussion on how hydrothermal conditions and treatment methods affect the morphology and microstructure. In the case of hydrothermal time <3 h or Ti source <0.05 ml, TiO2 nanorods become rarely on the glass substrate; in the case of hydrothermal time >3 h or Ti source >0.2 ml, TiO2 begins to grow in the disorder, surrounded and staggered. The longer hydrothermal time or the more Ti source, the more intensive and staggered the growth phenomenon of TiO2 nanorods becomes; in the case of hydrothermal time up to 12 h, they grow only along the normal direction of the glass substrate surface. Subsequently, electronic conductivity and charge storage capability for the treated TiO2 nanorods were evaluated and concentrated on capacitance behavior. The pristine TiO2 just achieves a specific capacitance of 2.24 F/g due to its low conductivity; however, a specific capacitance of 47.1 F/g was achieved for the TiO2 treated by hydrazine hydrate. This dramatic increase in specific capacitance is attributed to conductivity improvement after post-treatment, which is supported by a sharp Redox peak observed at similar to 0.4 V of CV for the treated TiO2 nanorods. Hydrazine treatment is an effective way to increase the pseudocapacitance performance of TiO2 nano transition metal oxides.

All-solid-state electrochemical energy storage systems offer higher energy density and improved safety. This study introduces an innovative technique for the in-situ production of nickel cobalt-layered double hydroxide (NCL) composites with Sakura-derived activated carbon (SAC) and sulfur (S) via a one-step hydrothermal process. Integrating NCL with S-doped SAC (SSAC) enhances conductivity, wettability, and active sites, improving electrochemical performance. The NCL-SSAC composite, characterized by its microflower architecture and nanosheets, facilitates rapid ion transport and maintains structural integrity. All-solid-state supercapacitors, both symmetric and asymmetric, were developed using a PVA-KOH-IL solid electrolyte. The NCL-SSAC//SSAC asymmetric supercapacitor achieved a specific capacitance of 360 F/g, an energy density of 160 Wh/kg, and a power density of 4.5 kW/kg. The device maintained 90 % capacitance after 20,000 cycles, demonstrated 96 % Coulombic efficiency, and successfully powered 27 light-emitting diodes for over 30 min. The results highlight the NCL-SSAC composite's ability to improve energy storage and stability in supercapacitors.

This study systematically investigated the regulation mechanisms of sintering temperature on the microstructure, defect characteristics, dielectric properties, and AC impedance behavior of SrTi0.995(Ta1/2Li1/2)0.005O3 ceramics. The results indicated that with the increase of sintering temperature, both the grain size and densification degree of ceramics gradually increased. Among the samples, the one sintered at 1450 degrees C exhibited the most optimized microstructure and superior dielectric properties. At 1 kHz and room temperature, this sample achieved a colossal permittivity of -105 with a low dielectric loss below 0.05, while maintaining excellent temperature stability over the range of -55 degrees C to 200 degrees C, fulfilling the EIA X9R standard. The outstanding dielectric properties was attributed to the optimized microstructure and the formation of defect dipoles as well as defect dipole clusters associated with oxygen vacancies, such as (TiTi)-Ti-y - V center dot center dot O - (TiTi)-Ti-y, Ta center dot Ti - V center dot center dot O - 3Ti(y)Ti, and (LiTi)-Ti-y - V center dot center dot O - Ta center dot Ti. These defect structures not only enhanced the material's polarization capability and permittivity but also effectively suppressed the long-range transport of charge carriers through the electron pinned defect dipole (EPDD) effect, thereby reducing dielectric loss.

The electrocaloric effect (ECE) represents an eco-friendly, solid-state cooling technique utilizing a safe and potent electric field to facilitate the refrigeration process. This research demonstrates that incorporating CoFe2O4 (CFO) and BiFeO3 (BFO) at a 1:1 mass ratio into P(VDF-TrFE) results in notable giant negative ECE at near room temperature and positive ECE in sandwiched composite films. With a 5 wt% addition of CFO and BFO, the composite films exhibited giant adiabatic temperature changes of 11.3 K at 374.4 K and-24 K at 316 K. Using the Landau model, we confirmed the occurrence of both positive and negative ECEs. We predicted an adiabatic temperature change as high as-37.2 K at an electric field of 120 MV m-1. The exceptional performance of the flexible, sandwiched composite films is attributed to their optimized microstructure and the strengthened local field around the dipoles, a result of the conductive CoFe2O4 and BiFeO3 nanoparticles. These dual-functional cooling films provide a means to boost the ECE in flexible materials, holding significant promise for applications in solid-state refrigeration tailored for flexible electronics. Future applications of the composite films may extend to various scenarios beyond the known multiferroic properties of BiFeO3 and the magnetic characteristics of CoFe2O4.

NiFe2O4 is a promising pseudocapacitive material owing to its multi-electron redox activity and chemical stability, yet its application is constrained by low conductivity, limited surface area, and sluggish ion diffusion. Here, we report a uniform magnetic-field-assisted hydrothermal strategy to optimize the microstructure and electrochemical performance of NiFe2O4. Unlike recent approaches such as carbon compositing, transition-metal doping, and template-assisted synthesis, which often involve complex procedures or high costs, our method provides a simple, scalable, and cost-effective pathway. By tuning the field strength, we reveal that a moderate field (1000 Gs) directs the assembly of ultrathin nanosheets into radially aligned "dandelion-like" microspheres while simultaneously enriching oxygen vacancies. This architecture enhances conductivity, accelerates ion diffusion, and increases redox-active sites. As a result, the NFO-1000 electrode achieves a specific capacitance of 295.8 F g-1 at 1 A g-1, an energy density of 21.2 Wh kg-1, and 95 % capacitance retention after 1000 cycles-representing a 90 % improvement compared to the zero-field sample. This work establishes moderate uniform magnetic fields as an efficient handle for defect engineering and mesostructural alignment, opening a new route for next-generation spinel-oxide-based energy storage devices.

The effect of doping O2 on the dielectric properties of the SrTiO3 (STO) ceramics was investigated in this work. Both semi-conductive and insulating STO ceramic samples were prepared using a two-step sintering method together with the tape casting technique. The structure and dielectric polarization properties of doping O2 on STO ceramics were studied by XRD, XPS, SEM, TEM, AC and DC electrical measurements. The experimental results indicate that: (1) When the temperature is below 900 degrees C, O2 cannot diffuse into the semi-conductive STO sample. However, when the temperature exceeds 1000 degrees C, O2 begins to penetrate through STO and the concentration of O2 increases with increasing temperatures; (2) O2 doping primarily occurs through grain boundaries rather than grain interiors. After doping with O2, the grain boundary resistance of STO increases, while the capacitance decreases rapidly. However, the grain resistance remains almost unchanged; (3) The diffusion of O2 has little effect on the change of grain resistance. On the contrary, as the grain boundary width increases with temperature, O2 diffusion can significantly reduce the capacitance of STO ceramics.

We designed novel BiFeO3/P(VDF-TrFE) gradient structures and spun coating composite films on a fluorinedoped tin oxide (FTO) conductive glass substrate. A large remnant ferroelectric polarization of 29.5 mu C/cm2, a 210 % improvement over the pure P(VDF-TrFE) film, is achieved by BiFeO3 nanoparticles embedment, with the coercive electric field Ec effectively restrained by 12 %. The structure analysis showed increased polar phase, reduced crystal size, and established long chains after BiFeO3 gradient incorporation, which are essential to the ferroelectric performances. The finite element simulation by COMSOL software illustrated an apparent potential redistribution up to 342 MV/m at an external electric field of 160 MV/m and large leakage currents around BiFeO3, which reflect the heterogeneous regions formed at the interfaces and they are contributive to the micromorphology. These gradient composite films have potential in the low electric field driving flexible electronic devices.

Increasing the insulation resistance is essential for improving the performance of the grain boundary layer capacitor of strontium titanate (SrTiO3, STO). Usually, the STO layered ceramic capacitor is fabricated using the two-step sintering method and the resistance can be largely enhanced during the insulating process at the second step by diffusing metallic oxides from the surface of STO ceramics at a high temperature around 1100 degrees C. In the work, a new approach is provided to enhance the insulation resistance of STO using the CuO/Al2O3 secondary sintering technique. It is found that with increasing the duration of the CuO/Al2O3 treatment, nano scaled CuO particles emerge at STO grain boundaries and the insulation resistance is hugely enhanced. An optimistic STO grain boundary layered ceramic capacitor with dielectric permittivity of 15075(1 kHz), loss of 0.043 (1 kHz) and insulation resistivity of 3.4 x 109 Omega m is obtained by the CuO/Al2O3 approach. It indicates that the CuO/Al2O3 secondary sintering technique is considerably effective to make high performance STO layer capacitors.

In this paper, we investigated the electrochemical behavior of cobalt ferrite based (CoFe2O4) and its effects on its electrical properties under magnetic field conditions. We prepared the CoFe2O4 pseudocapacitive anode material by hydrothermal method. The structure and morphology were characterized by XRD, SEM, XPS and VSM. The electrochemical behavior and electrical properties of CoFe2O4 were tested and analyzed by cyclic voltammetry (CV), constant current charge and discharge (GCD), and AC impedance (EIS) under magnetic field conditions. The results showed that the applied magnetic field significantly improved the specific capacitance, energy density, and charge transport efficiency of the CoFe2O4. Under 7000 Gs (0.7 T) magnetic field, the specific capacitance of CV test increases from 163.9 F/g at zero field to 243 F/g, the lift ratio is 48.3 %, and the corresponding discharge time extends from 98 s at zero field to 143 s, the lift ratio is 51 %. The analysis demonstrated that the magnetic field affects the electron transport and ion diffusion process of the electrode material. This improves the electrochemical properties of the CoFe2O4. This study proposes a novel strategy and provides experimental evidence for magnetic field-regulated optimization of pseudocapacitive electrode materials.

BiFeO3 has profuse physical properties in multiferroics. However, significant leakage current constrains its utility in practical applications. In this paper, we synergistically embed BiFeO3 nanoparticles in a ferroelectric crystal P (VDF-TrFE) base and use barrier layers to reduce the leakage current and promote the ferroelectric performance. Our finding indicate that the multilayer BiFeO3/P(VDF-TrFE) composite films equipped with barrier layers exhibit a leakage current below the magnitude of microampere level, a 99 % reduction compared to single-layer films. Additionally, the effective remnant ferroelectric polarization reaches 16 mu C/cm2, a 66 % improvement. We combined the conductive mechanism analysis by fitting I-V curves and constructing energy band structures, uncovering that the essence of the optimization characteristics is related to a Space-Charge-Limited Conduction (SCLC) mechanism in the multilayer composite films. This research offers potential film solutions for a variety of electrical devices, supported by both experimental and theoretical perspectives.

In the last decade, refrigeration technology based on electrocaloric effect (ECE) has become a research hotspot in the ferroelectric field, profiting from being environmentally friendly and highly efficient. In this paper, we fabricated CoFe2O4/P(VDF-TrFE) multilayer composite films on an fluorine-doped tin oxide glass by integrating CoFe2O4 additives and P(VDF-TrFE) barriers to innovate the structures and ECE performances. As a result, the multilayer composite films showed comprehensive superiorities such as higher crystallization, smaller grain size, more polar phase, smaller coercive fields, and higher polarizations than the reference P(VDF-TrFE) films. The composite films have acceptably low leakage currents far below micrometers at a high electric field of 100 MV m−1. We measured a giant ECE temperature change of 25.9 K and an ECE strength of 0.37 K m MV−1 at a relatively small external field of 70 MV m−1 for ferroelectric polymers, extremely competitive over the reported. The Landau–Devonshire theory ascertained the reliability of the ECE performance by the indirect method and predicted a high ECE temperature change of 54 K under 140 MV m−1 of the multilayer composite films. The giant ECE CoFe2O4/P(VDF-TrFE) multilayer composite films are prospective for solid-state refrigeration.