Search

In this work, the niobate-based borate glass-ceramic system K2O–Na2O–Nb2O5–B2O3 was proposed for the first time, in which the presence of alkali metal oxides not only tends to form ferroelectric crystalline phase to obtain high permittivity, but also optimizes the borate glass network structure to enhance the breakdown strength. The change of borate glass network structure and the influence on conductivity and carriers migrate is systematically discussed. The results show that the high breakdown performance is attributed to the transformation from [B∅2O−] triangle to [B∅4]- tetrahedron realizes the high extent of glass network polymerization, which effectively impedes carriers migration and reduces the conductivity. The high permittivity and low dielectric loss are obtained in the range of room temperature to 200 °C. Compared to other niobate-based glass-ceramics, the potassium sodium niobate borate glass-ceramic simultaneously achieve high discharge energy density, high power density and rapid discharge rate (∼14 ns).

Aiming at the problem that power density and energy density are difficult to obtain simultaneously under low field, a novel composition (1-x)Na0·5Bi0·5TiO3-xBaZn1/3Ta2/3O3((1-x)NBT-xBZT) was designed and fabricated via solid-state methods. With the addition of BZT, the crystal lattice, structural symmetry, grain size, and dense degree were all increased proved by XRD, Raman, and Archimedes drainage method et al. Because of the enhancement of relaxor behavior, the x=0.10 sample displayed a high permittivity er of 2871±15% and a low dielectric loss tan δ ≤ 0.025 in the wide temperature range of 60–400 oC. This ceramic also showed maximum recoverable energy density Wd (2.07 J/cm3) with high efficiency η (71.5%) under a low field of 150 kV/cm. Moreover, pulse discharge testing proved that this ceramic possessed both a significant discharge energy density WD (0.96 J/cm3) and a record high power density PD (108.54 MW/cm3). This work provided a promising material for high power and energy applications.

In this work, novel (1 [Formula: see text])(0.75Na[Formula: see text]Bi[Formula: see text]TiO3)-0.25Sr(Zr[Formula: see text]Sn[Formula: see text]Hf[Formula: see text]Ti[Formula: see text]Nb[Formula: see text])O3-[Formula: see text]NaNbO3 (NBT-SZSHTN-[Formula: see text]NN, [Formula: see text] = 0.1, 0.15, 0.2, 0.25) ceramics were fabricated. The influence of co-doping of NN and high entropy perovskite oxide (SZSHTN) on the phase structure, microstructure and dielectric properties of NBT-based lead-free ceramics was investigated. Dense microstructure with a grain size of [Formula: see text]5 [Formula: see text]m is observed. When [Formula: see text] = 0.25, a wide dielectric temperature stable range of −35.4–224.3[Formula: see text]C with a low temperature coefficient of capacitance of [Formula: see text] 10% is achieved, fulfilling the industry standard of Y9P specification. Furthermore, excellent energy storage performance with recoverable energy density of 2.4 J/cm3, discharge efficiency of 71%, power density of 25.495 MW/cm3 and discharge rate [Formula: see text] 200 ns are simultaneously obtained, which shows great potential for high temperature capacitor applications.

Bulk charge recombination is one of the main blocks to the photocatalytic efficiency. The internal electric field brought by ferroelectric polarization in ferroelectric materials and the decreasing transport distance of carriers by tailoring morphology have been proposed to overcome this problem. Herein, thin-sheet Na0.5Bi0.5TiO3 photocatalyst with strong ferroelectric polarization was prepared by topochemical molten salt synthetic (TMSS) method. Without co-catalysts, thin-sheet Na0.5Bi0.5TiO3 represented excellent photocatalytic performance that degradation efficiency towards RhB, tetracycline and ciprofloxacin were 99.8%, 76.6% and 68.3% under simulated sunlight within 100 min, respectively. P-E loops and XPS measurement demonstrated that thin-sheet shape led to a large number of atoms missing on the surface, resulting in lattice distortion, and the spontaneous polarization was greatly improved at the same time. The synergetic effect of strong ferroelectric polarization and thin-sheet shape of Na0.5Bi0.5TiO3 promoted the separation of photo-generated carriers in the bulk. This work proved that single ferroelectric materials possessed glorious ability for photocatalytic reaction via minishing the thickness and enhancing the degree of distortion to build strong internal electric field.

Dielectric ceramics with excellent discharge properties and high-temperature stability are promising and challenging for pulse power applications. In the present work, novel (1 − x)Na0.5Bi0.5TiO3–xBaMg1/3Ta2/3O3 ((1 − x)NBT–xBMT) ceramics were designed and fabricated, which showed a high permittivity er of 2102.688 ± 15% at 24–377 °C and a low dielectric loss tan δ ≤ 0.02 at 34–299 °C in x = 0.15 sample. After BMT modification, the NBT ceramics showed a nearly cubic tolerance factor of 1 and enhanced relaxor behavior. Consequently, a significant energy storage density Ws ~ 2.8 J/cm3 with high efficiency η ~ 78.67% was obtained in x = 0.15 sample at 175 kV/cm. Furthermore, pulse discharge testing demonstrated that this ceramic sample exhibited a satisfying discharge energy density WD ~ 0.88 J/cm3, a high power density PD ~ 59.07 MW/cm3 and a fast discharge speed (~ 50 ns) up to operating temperature of 170 °C, superior to most lead-free ceramics. The present work provides a novel composition with superior discharge properties.

The (1-x)BaTiO3-xCuO ceramics (x = 0, 0.5, 1.0, 1.5 and 2.0 wt%) were prepared by the traditional solid-state reaction method. The influence of the distribution of Cu-rich phase on the microscopic morphology, dielectric and complex impedance of BaTiO3 was studied. All samples show tetragonal phase structure. The images of SEM and EDS show that different amounts of CuO result in diverse distribution of Cu element at the grain boundary. The Cu element is concentrated in the grain boundary in a continuous network structure for x = 1.0 wt% and x = 2.0 wt%. And the Cu elements are mainly distributed in the punctate structure at triple junction for x = 1.5 wt%. Due to the pinning effect of Cu-rich phase at the triple junction, the grain of the BaTiO3 is refined. Not only is it beneficial to increase the permittivity and reduce the dielectric loss, but also improve the frequency stability of the dielectric performance at low frequency. In addition, the impedance analysis shows that the resistance and activation energy of conductivity of (1-x)BaTiO3-xCuO ceramics depend on the synergistic effect of the grain size and Cu-rich phase at the grain boundary. The smaller grain and the more Cu-rich phase at grain boundary, the greater resistance and activation energy of conductivity.

Lead-free antiferroelectric (AFE) materials have seen a surge of research activity in environmentally friendly energy storage technologies. Recently, considerable work has been done to improve the stability of AFE in NaNbO3 (NN) ceramics, but it remains a grand challenge to obtain typical AFE characteristic double P-E loops in NN ceramics at ambient conditions. In a preliminary estimate of tolerance factor versus average electronegativity difference, we reported the stable AFE phase in 0.95NaNbO3-0.05BiMg2/3Ta1/3O3 sample. The orthorhombic Q to P phase transition was verified by XRD and TEM. Then, the remarkable double P-E loops were obtained in 0.95NaNbO3-0.05BiMg2/3Ta1/3O3 ceramics. Furthermore, a phenomenological model was proposed to explain the P-E relationships and our results. Compared with other reported compounds, the TP-R decreased more obviously from 350 °C to 200 °C. Superior temperature stability (variations of maximum current, current density, and power density within 15% over 30–140 °C) and field induced phase transition were also confirmed by the pulse charge testing. Our work develops a new road for achieving room-temperature double P-E loops in NN ceramics by BiM1M2O3 (M1 might be Mg, Zn, etc; M2 might be Nb, Ta, etc) additives.

For the urgent demand of environmental protection and energy conservation, it is of great significance to develop environmentally-friendly dielectric ceramics with outstanding characteristic of energy storage and quick charge discharge capacity. For this study, we applied a strategy to achieve the enhancement of energy storage performance in (Ca0.5Sr0.5)1-xMgxTiO3 (abbreviate as CSMTx, x = 0.005, 0.010, 0.020, 0.040) linear ceramics based on the introduction of Mg2+ ion. Scanning electron microscopy and complex impedance measurement reveal that Mg2+ ion doping can refine grain size and increase grain boundary density, which results in grain boundary barrier strengthening owing to high-resistance grain boundaries. As a result, the marvellous energy storage properties, including an ultrahigh recoverable energy density of 2.88 J/cm3 combined with a giant energy efficiency of 90% are concurrently obtained in (Ca0.5Sr0.5)0.99Mg0.01TiO3 ceramic at an enhanced breakdown field (460 kV/cm). Meanwhile, this composition ceramic also exhibits the superior stability of frequency (1–1000 Hz) and temperature (20–100 °C) with minimal variation. In addition, the actual performance of ceramic capacitors in operation can be evaluated via the pulsed charge-discharge process. Delightedly, the superfast discharge speed (t0.9 = 20.4 ns), large current density (CD) of 421.23 A/cm2 and ultrahigh power density (PD) of 25.27 MW/cm3, as well as prominent thermal stability (20–100 °C) are synchronously produced in the CSMT2 ceramic. These merits qualify the unleaded linear ceramic as a competitive candidate for high-power capacitor applications, which offers a practicable approach for exploration on high-performance dielectric materials.

Glass-ceramics possessing high power density, energy density and fast charge-discharge rate during a wide temperature range are considered to be the ideal materials for pulse power applications. Under the premise of negligible effect on the glass network structure, the energy storage performance was improved by introducing Na+ ions, which reduced the carrier mobility and the conductivity in this study. The potassium sodium niobate silicate initial glass were synthesized by the traditional melting method, and the glass-ceramics were prepared by the crystallization treatment at 800 °C for 2 h. Introducing sodium ions promoted the formation of Na0.35K0.65NbO3 phase, and increased the permittivity to 104 simultaneously. Superior high breakdown strength (750 kV/cm) was obtained because of the competition between two physical mechanisms of electrical conductivity and micromorphology. When the sodium oxide content was 0.375, the discharge energy density of 2.44 J/cm3 and high energy storage efficiency of 93% were obtained. Compared with ceramics, polymers and other niobate-based glass-ceramics reported currently, this work had achieved high actual discharge energy density (0.156 J/cm3) and high power density (19.6 MW/cm3) under low field strength, and had an extremely fast discharge rate (~14 ns) and excellent wide temperature stability (20–120 °C).

The pulse discharge characterization of perovskite dielectric ceramics, which has confronted a barrier between research and application, has the problems of inconsistent test standards and lack of comparability. To mitigate this issue and further advance the application process, we suggest an extrinsic standard (for convenience of comparison) for energy dielectric ceramics of thickness (0.2 mm), electrode area (4 mm2) and operation voltage (2 kV). We report the pulse discharge performance parameters of three typical dielectric materials: relaxor ferroelectric (Na0.5Bi0.5)0.9Li0.1Ti0.9Ta0.1O3 (NBLTT), paraelectric Ca0.6Sr0.4TiO3 (CST) and linear dielectric K0.5Na0.5NbO3 (KNN) glass ceramics through computer simulation and fitting of pulse discharge curves based on the resistance-inductance-capacitor pulse discharge circuit. The NBLTT ceramics exhibited higher peak current (16 A under 100 kV/cm) and stability with minimal variation less than 15% from 20 to 150 °C during pulse discharge compared with linear dielectric and ferroelectric glass ceramics. In addition, the NBLTT system holds the fast discharge time (90% of the discharge energy density released in about 100 ns) and good fatigue resistance. The short discharge time, high thermal stability and low medium voltage (500–5000 V) make the NBLTT ceramics promising for pulse capacitor in large current and low electric operation voltage conditions. An operable comparison standard and the research frontiers of pulsed dielectric materials are prospected.

BiOBr sheets of controllable shape and size were synthesized via an ultrasound-assisted co-precipitation method at room temperature by varying the bromine source and reactant concentration. The BiOBr sheets synthesized from KBr and NaBr were rounded rectangles and round, respectively. The size of BiOBr sheets increased with increasing reactant concentration. As the reactant concentration increased from 10 mmol L−1 to 15 mmol L−1 until 20 mmol L−1, the size of as-prepared BiOBr sheets increased from 100–300 nm to 300–500 nm until 700–1000 nm, respectively. Moreover, the size difference in BiOBr sheets did not significantly affect the photocatalytic performance in degrading organic dyes. Such a simple and rapid method of controlling the shape and size of BiOBr sheets could provide more abundant matrix materials for the synthesis and modification of BiOBr.

The relationship between enhanced dielectric property and structural distortion in tungsten bronze structure ceramics was discussed in this work. The ceramics with the composition of (Ba1-xCax)2NaNb5O15 (x = 0, 0.1, 0.2, 0.3, 0.4) were fabricated via conventional solid-state method. All ceramics were pure without secondary phase and the distinct lattice distortion in structure was testified by Rietveld XRD refinement. Compared with the un-doped composition, the maximum polarization and energy storage density were strongly enhanced according to the ferroelectric property measurements, which were contributed to the distortion of NbO6 octahedron induced by the variation of ionic radius. The actually pulsed charge-discharge property of x = 0.3 ceramic was tested, whist excellent power density (PD = 35.106 MV/cm3) and discharge energy density (Wd = 0.29 J/cm3) were obtained at 100 °C under 120 kV/cm, revealing the potential for application of Ba2NaNb5O15 system-based ceramics in harsh environment.

The excellent energy storage and pulse charge-discharge performance ceramics with high temperature stability and optical transmissivity are competitive for the development of electronic devices. In this work, comprehensive improved performances are simultaneously realized in DyxSr1-xTiO3 (DST) ceramics through defect and interface engineering. Meanwhile, increased high insulation grain boundary and reduced carrier mobility promote the increase of grain boundary resistance, and the increase of grain resistance primarily originates from the fact that D y T i ' can easily attract oxygen vacancy, forming defect dipoles and restraining the movement of oxygen vacancies. Additionally, the relative density of ceramics is increased by sintering in O2 and doping Dy ions. Hence, x = 0.008 ceramics exhibit high coverable energy storage density of 4.00 J/cm3, high energy storage efficiency of 89.49%, excellent frequency (1Hz-1 kHz) and temperature stability (20-120 °C) and transmittance of >60% are achieved at 510 kV/cm at 0.2 mm. Furthermore, x = 0.008 ceramics possess the prominent current density of 420.1 A/cm2 and the prominent power density of 19.2 MW/cm3. Meanwhile, the short discharge rate of 20 ns and excellent stability of temperature (20-120 °C) are also achieved, suggesting that it is one candidate with strong potential for the application of lead-free high power capacitors.

Colossal permittivity (CP) ceramics have a great potential in the development of miniaturization, integration and lightweight of electronic components. In this work, NdxSr1-xTiO3 (0.000 ≤ x ≤ 0.014) (NST) ceramics are successfully prepared via sintering in N2. Simultaneously microstructure and dielectric properties of NST ceramics are characterized. It can be found that 0.010 ≤ x ≤ 0.014 ceramics show CP (>20000, 20–1 × 106 Hz) and low dielectric loss ( T i T i ' , N d S r ⋅ , V O ⋅ ⋅ ) forms the defect dipoles ( Ti Ti ' − N d S r ⋅ , T i T i ' − V O ⋅ ⋅ − T i T i ' ) and the defect clusters ( V O ⋅ ⋅ − 3 T i T i ' − N d S r ⋅ ), which produces the electron pinning effect and restricts the long-range movement of the carriers. Additionally, the grain boundary with high insulation resistivity plays a major role in the resistance of ceramics, and it also acts as a high barrier layer to limit the movement of several delocalized carriers.

(1-x) (K2O–Na2O–2Nb2O5)-x (2BaO–Nb2O5–2SiO2) glass-ceramics with x = 0.10, 0.15, 0.20, 0.25 have been successfully prepared by traditional melting method. XRD and microstructure analysis demonstrate that all glass-ceramics are crystallized into uniform Na0.9K0.1NbO3 and K2(NbO)2(Si4O12) ferroelectric crystalline phase. Increasing x promotes the formation of Ba2NaNb5O15 phase with a tungsten bronze structure. Raman and complex impedance data confirmed that Ba2+ is introduced to repair the disruption of the glass network and make carrier migration difficult when x = 0.15. Thus, the x = 0.15 glass-ceramic sample possesses a maximum calculated energy storage density of 2.32 J/cm3 under 820 kV/cm because of a high degree of polymerization (DOP) glass network structure. Moreover, the pulsed discharge-charge tests are carried out to evaluate actual energy storage performance.

High performance colossal permittivity (CP) ceramic materials are indispensable for the development of electronic devices. In this work, excellent Sr1-xDyxTiO3 (0.000 ≤ x ≤ 0.018) ceramic samples were prepared through a traditional solid phase method. It can be found that the insulation resistivity of 4.7 × 107 Ω/cm3 (DC 100V), the CP of 26712 and the low dielectric loss of 0.0065 (1 kHz) are obtained in x = 0.008 ceramic samples sintered in N2. Based on the analysis of XRD, XPS and comparison of sintering in different atmospheres, the excellent dielectric property is mainly determined by defect dipoles associated with oxygen vacancy (eg. Ti Ti ' − V O ⋅ ⋅ − Ti Ti ' ). These defect dipoles limit the long-range transition of electrons and result in electronic pinning effect. Additionally, it can be perceived that the insulation resistivity of 1.12 × 109 Ω/cm3 (DC 100 V), the CP of 23134 and the low dielectric loss of 0.0098 (1 kHz) are achieved in x = 0.008 ceramic samples after reoxidation. According to the analysis of complex impedance spectroscopy, the improvement of the insulation resistivity of x = 0.008 ceramic samples is mainly attributed to the increase of the grain boundary resistance.

The high energy density and power density dielectric ceramics with wide frequency and temperature stability are competitive materials for pulse power capacitors. This research proposes an effective strategy for enhancing energy storage performance of Ca0.5Sr0.5TiO3 ceramics through the introduction of Sn4+ ion. This ion restrains grain growth, increases high insulating grain boundaries, and thus enhances the barrier height of grain boundaries, which are demonstrated in SEM micrographs and complex impedance. The Ca0.5Sr0.5Ti0.97Sn0.03O3 (SnCST3) ceramics possess high energy storage density of 2.06 J/cm3 and efficiency of 95% under breakdown strength of 330 kV/cm, which get benefit from wide band gap of 5.3 eV. While the exceptional stability with minimal fluctuation (

The present work investigates the influence of donor doping and its concentration on the flash sintering behavior of barium titanate. The characteristic of non-ohimic conductivity during flash event shows that flash sintering is associated with dielectric breakdown due to the similar physical phenomena. The polarization of dielectric particle contributes to the enhancement of local electric field strength. The magnified electric field caused by local charges accumulation gives rise to dielectric breakdown phenomenon during flash sintering. The SEM measurement indicates an obvious breakdown channel through the inside of sample, which provides a convincible evidence for dielectric breakdown. In addition, the impacts of temperature and field on carrier activation and migration are emphasized. Eventually, the non-ohmic conductivity can be explained by the physical phenomenon of dielectric breakdown described by Poole-Frenkel Emission.

A series of high entropy Ba(Zr0.2Ti0.2Sn0.2Hf0.2Me0.2)O3 (Me=Y3+,Nb5+,Ta5+,V5+,Mo6+,W6+) perovskite oxides were synthesized by using a solid state reaction method. Three multiple-cation solid solutions formed pure phase compounds, and only two compounds were sintered into ceramics. Microstructure analysis showed the influence of configurational entropy on phase stability and grain growth. Dielectric measurements showed that the high entropy ceramics possessed decent temperature stability of permittivity from 25 °C to 200 °C, low dielectric loss (

SrBi2Nb1.8−xCoxFe0.2O9 (SBCFN, x = 0, 0.1, 0.2, 0.3 and 0.4) ceramic samples were fabricated by traditional solid-state reaction. Structure was detected by XRD and SEM, which demonstrated that all samples showed pure orthorhombic Aurivillius structure and the plate-like grains were observed. The morphology gradually disappeared with Co ions doping. Relaxation peak in low-temperature region of Co-doped samples was discussed in dielectric spectra. Besides, the decrease in resistance induced by the motion of first ionized oxygen vacancies was revealed by fitted Arrhenius curves and supported by Correlated Barrier Hopping conduction model. The contribution of leakage current in P–E loops was observed. The optimum magnetic property was obtained when the molar ratio of Fe3+ and Co3+ is 1:1, which is attributed to introduction of double exchange interaction (Fe–O–Co). At the same time, the Eg was narrowed due to hybridization and lattice distortion, which was coincident with the result of resistance.