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The migration of dopants and oxygen vacancy (VO) significantly affect the temperature stability and insulation degradation behavior of BaTiO3-based dielectric ceramics. In this work, the improved dielectric properties and reliability are achieved in (Ba, Ca)TiO3 (BCT)-based ceramics due to the intriguing effect of Ca substitution. Theoretical calculations and experiments reveal the underlying mechanisms in the migration of dopants and VO. The migration barrier of dopants is increased by ∼0.02 eV or less due to the lattice shrinkage, while it is decreased by ∼0.5 eV due to the interatomic space expansion effect caused by the small size of Ca. Thus, the core–shell structure is more susceptible in BCT-based ceramics with higher Ca content. The VO is confirmed to be more stable near the Ca ion, forming the [CaBa-VO]·· defect complex. However, the migration barrier is significantly decreased among the first nearest O sites of Ca due to the enlarged space near Ca ion. Thus, the activation energy of VO and insulation degradation behavior are improved in BCT-based ceramics with moderate Ca content but deteriorate with high content, in which the intragranular migration channels with the low barrier are formed. The present results reveal the significant effect of Ca substitution on the migration of dopants and VOs, and further on the dielectric temperature stability and reliability. [ABSTRACT FROM AUTHOR]

The fast recombination of photogenerated electrons and holes remains a major issue in hindering photocatalytic efficiency. Apart from traditional methods, such as rare metal deposition and element doping, the introduction of a built‐in electric field has been proven an efficient way in recent years. Ferroelectrics, which possess spontaneous polarization and associated polarization electric fields, are attracting more attention as photocatalysts. In this study, Bi2MoO6 spheres with different hierarchical upper nanostructures are synthesized through a one‐pot hydrothermal method. With this porous structure and the intrinsic ferroelectricity, BMO spheres present excellent physisorption and photodegradation ability toward dye molecules. After corona poling treatment, the ferroelectric field of the BMO samples was enhanced, and the recombination of charges was suppressed, leading to an obvious increase in photocatalytic rate. The origin BMO‐5 can reach a total degradation of RhB in 20 min, and the polarized BMO‐5 (BMO‐5P) can remove all RhB molecules instantly through the physisorption process. Apart from BMO‐5, other samples also present excellent catalytic behavior. Origin BMO‐2 can fully degrade the RhB in 40 min, and the degradation time of polarized BMO‐2P is 30 min. The hierarchical structure and internal polarized electric field endow BMO spheres with outstanding adsorption purification and photodegradation ability and provide a new comprehensive strategy for the catalyst design. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman scattering (SERS) is an ultrasensitive spectroscopic analysis technique widely used for molecule detection. However, manufacturing uniform, stable, and ultrasensitive substrates remains a challenge for the practical application of the SERS technology. Precious metals and semiconductors have been proved to be attractive and universal for SERS detection. In this work, a facile strategy is applied to prepare uniform three‐dimensional (3D) Ag@TiO2 nanostructures as SERS sensors. The Scanning electron microscopy and X‐ray photoelectron spectroscopy results indicate that silver nanoparticles are uniformly deposited into the pores of the TiO2 nanocavity arrays. The 3D hybrid substrate presents highly sensitive SERS signals of 4‐mercaptobenzoicacid (4‐MBA) with a detection limitation as low as 10−17 M. To prevent the oxidization of Ag and keep the activity of the film, a polymer mask was deposited on the SERS substrate and brought about excellent stability after weeks of reserving in air. In a nutshell, a SERS substrate with a high sensitivity and stability as well as good uniformity has been successfully developed in this work, which has a potential application for high‐precision SERS detection. [ABSTRACT FROM AUTHOR]

The defect mechanisms of rare earth (RE) doped BaTiO3 have a strong impact on the electrical performance of the multilayer ceramics capacitors (MLCCs). Oxygen vacancy is the main reason for the device degradation over longtime use, while the effect of the doping strategy on controlling the oxygen vacancies is not yet quantitatively understood. In this work, the grand canonical thermodynamic defect model based on first‐principle calculations is applied to evaluate the defect mechanism of RE‐doped BaTiO3 under practical experimental condition. The charge compensation and prior site occupancy of RE are found not only associated with ionic size but also exhibit transitions with oxygen partial pressure and doping concentration. Furthermore, the oxygen vacancy trapping ability of RE ions is evaluated from the perspectives of thermodynamics and kinetics. The migration barrier among first nearest oxygen sites dramatically changed depending on the RE site occupancy. The large trapping ability is contributed by the relatively large negative binding energy of the defect complex and comparable RE concentrations substituted on Ba and Ti sites. The two conditions can be achieved in amphoteric ions doped systems, while in pure donor doped BT only one of these conditions can be satisfied. Although the self‐compensated defect complexes exhibit the highest binding energy, the trapping ability contributed by different defect complexes (RETi′${\rm{RE}}_{{\rm{Ti}}}^{\rm{^{\prime}}}$, REBa·${\rm{RE}}_{{\rm{Ba}}}^ \cdot $, REBa − RETi) is generally comparable in these systems. This feature of amphoteric RE ions accounts for the improvement of the lifetime and reliability of MLCCs. [ABSTRACT FROM AUTHOR]

The black TiO2 nanotubes arrays were prepared by anodizing and aluminothermic reduction process. The prepared samples were characterized by X‐ray diffraction (XRD), SEM, UV‐visible absorption spectroscopy and X‐ray photoelectron spectroscopy (XPS). The photochemical/electrical catalytic activity of the samples before and after blackening treatment was tested. Comparing with the raw TiO2, the macrostructure of the black TiO2 nanotube arrays changes a little, and the tubal walls become a little thicker and rough. The photocatalytic hydrogen production rate has an obvious enhancement (from 8.9 µmol cm−2 h−1 to 22.8 µmol cm−2 h−1) after the blackening treatment and the electrocatalytic H2 evolution rate is also improved with a lower onset potential. The increment of trivalent Ti3+ on the surface is confirmed by XPS and presented by the colour changing of the samples (from white colour to black). The hybrid energy band gap and reduced charge transfer barrier are proved to be essential in promoting the catalytic properties of the black TiO2 nanotube arrays. [ABSTRACT FROM AUTHOR]

We fabricated x(Bi0.5Na0.5)TiO3–(1−x)[BaTiO3–(Bi0.5Na0.5)TiO3–Nb] (BNT‐doped BTBNT‐Nb) dielectric materials with high permittivity and excellent high‐temperature energy storage properties. The initial powder of Nb‐modified BTBNT was first calcined and then modified with different stoichiometric ratios of (Bi0.5Na0.5)TiO3 (BNT). Variable‐temperature X‐ray diffraction (XRD) results showed that the ceramics with a small amount of BNT doping consisted of coexisting tetragonal and pseudocubic phases, which transformed into the pseudocubic phase as the test temperature increased. The results of transmission electron microscopy (TEM) showed that the ceramic grain was the core‐shell structure. The permittivity of the 5 mol% BNT‐doped BTBNT‐Nb ceramic reached up to 2343, meeting the X9R specification. The discharge energy densities of all samples were 1.70‐1.91 J/cm3 at room temperature. The discharge energy densities of all samples fluctuated by only ±5% over the wide temperature range from 25°C to 175°C and ±8% from 25°C to 200°C. The discharge energy density of the 50 mol% BNT‐doped BTBNT‐Nb ceramic was 2.01 J/cm3 at 210 kV/cm and 175°C. The maximum energy efficiencies of all ceramics were up to ~91% at high temperatures and were much better than those at room temperature. The stable dielectric properties within a wide temperature window and excellent high‐temperature energy storage properties of this BNT‐doped BTBNT‐Nb system make it promising to provide candidate materials for multilayer ceramic capacitor applications. [ABSTRACT FROM AUTHOR]

With the miniaturization of multilayer ceramic capacitors (MLCCs) and the increase of the electric field on a single dielectric layer, dielectric constant DC-bias stability and reliability have gradually aroused attention in the advanced electronics industry. In this study, MLCCs with outstanding DC-bias stability and reliability were prepared by using dielectric ceramic optimization and electrode optimization strategies. The effect of the Dy-Y doping concentration on the microstructure, dielectric properties, and reliability of BaTiO 3 -based ceramics was investigated. The shell ratio and effective shell doping concentration of the core-shell structure in ceramic grains play important roles in defects and electrical performances. The ceramic with appropriate doping contents shows a dielectric constant of 1800 and a dielectric constant change rate of -17% under a DC field of 4 kV/mm, which was fabricated into prototype MLCCs with different Ni electrodes. MLCCs exhibit outstanding DC-bias stability with a -28% degradation in the dielectric constant under a DC field of 4 kV/mm while possessing a dielectric constant of 2300 and satisfying the EIA X7S specification. Additionally, it was discovered that MLCCs prepared by using fine-size Ni particle electrodes have low electrode roughness and high interfacial Schottky barriers, resulting in better reliability. This study provides promising candidate materials and theoretical references for high-end and high DC-bias stability MLCCs.

Low energy conversion efficiency from the absorbed photon to the catalytic species remains a major obstacle for the real application of photocatalysis. In recent years, the introduction of a built-in electric field has proved to be impactful in facilitating the photoinduced charge separation, among which, ferroelectric polarization is highly recommended by getting rid of mechanical stresses. Developing ferroelectrics directly as photoactive semiconductors is promising in view of the synergistic catalytic enhancement. Therefore, Bi 2 MoO 6 nanosheets with ultrathin layered structure (<10 nm) and abundant oxygen vacancies were synthesized through the hydrothermal method. The two-dimensional nanostructure created more active sites and a convenient polarization condition. Subsequently, corona poling was applied on the Bi 2 MoO 6 nanosheets, which can significantly accelerate the 100% degradation rate of RhB from 50 to 20 min, surpassing that of metal-free photocatalysts. The combined effect of semiconductor, ferroelectric polarization, oxygen vacancies, and nano-layered structure offers new strategies for designing multifield coupling catalysts, providing insights into the regulation of charge carrier dynamics.