Y5U multilayer ceramic capacitors with high-specific capacitance and low-equivalent series resistance

A dielectric powder material, for Y5U multilayer ceramic capacitors was developed in the Pb(Mg(1/3)Nb(2/3))O (3)-Pb(Ni(1/3)Nb(2/3))O(3)-PbTiO (3) ternary system by using an alkoxide process. Multilayer ceramic chip capacitors (10 muF) with high specific capacitances were fabricated using this powder. A Ag80%-Pd20% alloy was used for the internal electrodes. The alkoxide-derived capacitor had an extremely high specific capacitance of about 500 muF/cm(3) and a small temperature dependence meeting Y5U specifications of the EIA standard. The equivalent series resistance was approximately 20 mOmega at 500 kHz. The breakdown voltages of the capacitor were 300 V or higher. In accelerated load life tests and load humidity tests, no degradation of insulation resistance was found during 1000 h of testing.     

Low-content core–shell-structured TiO2 nanobelts@SiO2 doped with poly(vinylidene fluoride) composites to achieve high-energy storage density

Polymer film capacitors have a high power density and great application potential in high-power electronic devices; however, high-energy storage density of polymer composites is usually obtained via doping high-content ceramic filler. An efficient approach to solve this issue is to dope polymers with an ultralow-content ceramic filler to improve their energy storage density. In this work, one-dimensional (1D) TiO₂ nanobelts@SiO₂ (TO nb@SO) are prepared via the hydrothermal reaction, muffle calcination, and hydrolysis. Extremely low-content TO nb@SO/poly(vinylidene fluoride) (TO nb@SO/PVDF) composites are prepared. The microstructure, crystalline structure, dielectric properties, electric breakdown strength, and discharge energy density are systematically investigated. The results show that the nanobelts have a width of 250 nm, a length of 1–2 μm, and a uniform shell layer at the edge with a thickness of ～25 nm. The relative dielectric constant of the composites is significantly enhanced; it reaches 11 for PVDF at 100 Hz, and 12.03 for 0.5 wt% TO nb@SO/PVDF. The theoretical dielectric constant is calculated based on a mathematical model and compared with the measured value. 1D materials with a large aspect ratio are beneficial in the improvement of the dielectric properties. The Weibull breakdown field strength is 381.3 MV/m for 0.5 wt% TO nb@SO/PVDF. A discharge energy density of 8.86 J/cm³ is obtained at 390 MV/m, while a high charge/discharge efficiency of 66.28% is achieved. To conclude, this work provides a valuable method for increasing the energy storage density and charge/discharge efficiency of dielectric capacitors.

     

Thin film ferroelectrics for capacitor applications

Pulsed laser deposition (PLD) has been used to fabricate simple thin film capacitor structures with a variety of ferroelectric materials. Thin film capacitors using the conventional ferroelectric material BaxSr1-xTiO3(BSTO) have been made across the entire compositional series. Electrical characterization shows that in thin film form these ferroelectrics display Curie point behaviour which is largely independent of composition. This contrasts sharply with bulk behaviour. The thin film fabrication and characterization of relaxor ferroelectric ceramics, such as Pb(Mg1/3Nb2/3)O3 (PMN) and Pb(Zn1/3Nb2/3)O3-BaTiO3(PZN-BT), is also reported. © 1998 Chapman & Hall     

SrCO3掺杂对PMN-PMnN-PZT-Ce压电陶瓷储能及介电弛豫性能的影响

通过铌铁矿先驱法制备了Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)+xSrCO_3(PMN-PMnN-PZT-Ce-xSr,x=0.00,0.03,0.05,0.07)四元系压电陶瓷,研究了SrCO_3含量的变化对Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)-Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)(PMN-PMnN-PZT-Ce)压电陶瓷相结构、储能密度以及弛豫行为的影响。通过XRD表明,样品为单一稳定的钙钛矿结构,并且存在准同晶界(MPB);当x=0.07时,在外加电场60kV/cm下取得较好的储能性能:储能密度W1=0.31J/cm~3,储能效率η=0.47;通过修正Curie-Weise定律,较好地描述了陶瓷弥散相变的特征,弥散相变系数γ随着Sr~(2+)掺杂量的增加而增加。当x=0.07时,γ取得最大值1.972 8,此时弛豫现象最明显。     

新型超级电容器电极材料

超级电容器以其高功率、长周期使用寿命、环保等独特性能受到人们的广泛关注。决定超级电容器电荷存储的最关键因素是电极材料的特性。首先简要介绍了电容器的电荷储存机理。其次详细介绍了金属有机骨架材料(MOFs)、共价有机骨架材料(COFs)、二维过渡金属碳(氮)化物(MXenes)、金属氮化物(MN)、黑磷(BP)和有机分子电极材料等有望获得高能量密度和功率密度的新兴电极材料,以及最新制作的对称/非对称超级电容器的能量、电容、功率、循环性能和倍率性等参数。研究表明,COFs有望成为新一代廉价、绿色、可持续、多功能的储能装置的有机电极候选材料,其电化学性能仍有很大的提高空间。重点介绍了MOFs、COFs、MN、BP及近年来新型有机电极材料在超级电容器中的应用。最后,对超级电容器未来的发展和关键技术的挑战进行了展望。     

Multilayer Lead‐Free Ceramic Capacitors with Ultrahigh Energy Density and Efficiency

The utilization of antiferroelectric (AFE) materials is thought to be an effective approach to enhance the energy density of dielectric capacitors. However, the high energy dissipation and inferior reliability that are associated with the antiferroelectric–ferroelectric phase transition are the main issues that restrict the applications of antiferroelectric ceramics. Here, simultaneously achieving high energy density and efficiency in a dielectric ceramic is proposed by combining antiferroelectric and relaxor features. Based on this concept, a lead‐free dielectric (Na_0.5Bi_0.5)TiO₃‐x(Sr_0.7Bi_0.2)TiO₃ (NBT‐xSBT) system is investigated and the corresponding multilayer ceramic capacitors (MLCCs) are fabricated. A record‐high energy density of 9.5 J cm^?3, together with a high energy efficiency of 92%, is achieved in NBT‐0.45SBT multilayer ceramic capacitors, which consist of ten dielectric layers with the single‐layer thickness of 20 µm and the internal electrode area of 6.25 mm². Furthermore, the newly developed capacitor exhibits a wide temperature usage range of ‐60 to 120 °C, with an energy‐density variation of less than 10%, and satisfactory cycling reliability, with degradation of less than 8% over 10⁶ cycles. These characteristics demonstrate that the NBT‐0.45SBT multilayer ceramic is a promising candidate for high‐power energy storage applications.     

信息功能陶瓷研究的几个热点

信息功能陶瓷是具有电、磁、声、光、热、力、化学或生物等不同性能之间相互转化和耦合效应的一类无机非金属功能材料, 亦称为功能陶瓷或电子陶瓷, 主要包括介电、铁电、压电、热释电、半导体、电光、磁性、高温超导等多种功能的新型高技术陶瓷。基于各种功能效应的新一代电子元器件如: MLCC电容器、片式电感器、电阻器、PTC和NTC热敏电阻、变阻器、晶界层电容器、滤波器、谐振器、压电换能器、驱动器、微位移器等等, 它们是计算机、集成电路、移动通信、能源技术和军工电子等领域的重要基础材料与元器件。随着高新技术的快速发展, 功能陶瓷材料的发展趋势是多层化、低维化、复相化、织构化以及高均匀性、低成本、低温合成、环境协调; 新型元器件则朝着片式化、微型化、模块化、低功耗、高频化、智能化、绿色化、大功率以及在极端条件下服役的高可靠性方向发展。 　　近几年来, 随着人们环境保护意识的日益增强, 经济发展对能源需求的快速增长以及环境污染问题的日益突出, 环境友好型的无铅压电陶瓷、储能介质与高性能电容器、巨电卡效应成为功能陶瓷研究的三大热点。 1 d₃₃ > 400 pC/N的铌酸钾钠基无铅压电陶瓷 　　目前, 无铅压电陶瓷主要有BaTiO₃、Na_0.5Bi_0.5TiO₃和K_0.5Na_0.5NbO₃(KNN)三大体系, 其中BaTiO₃和Na_0.5Bi_0.5TiO₃的压电性能和居里温度相对较低, 主要用于超声探测器; KNN的烧结温度较低、居里温度高、压电系数高, 有望成为PZT的替代材料^[1-2]。 　　当K/Na=47/53时, KNN体系中存在两种正交相的相界, 此处的压电性能最优^[3]。从高温降低的过程中, KNN体系经历立方→四方→正交→三方等系列相变。三个介电峰位于690、480和158 K, 分别对应C-T、T-O和O-R三个相变。通过元素的掺杂取代可以改变KNN中的相变温度, 提高其铁电和压电性能。等价掺杂中A位通常掺杂一价的Li⁺或Ag⁺, B位掺杂五价的Ta⁵⁺或Sb⁵⁺; 不等价掺杂时, A位可以掺杂Ca²⁺、Sr²⁺或Ba²⁺, 甚至可以共掺(Bi_0.5Li_0.5)²⁺、(Bi_0.5Na_0.5)²⁺或(Bi_0.5K_0.5)²⁺, 此时B位可以有Ti⁴⁺和Zr⁴⁺。 　　研究发现Li⁺是唯一能够提高T_c的掺杂元素, 价态不匹配会导致T_c的迅速下降^[4]。T-O和O-R相变受到B位离子的强烈支配。B位Ti⁴⁺离子取代时会导致T-O和O-R相变温度降低^[5]。当B位被Zr⁴⁺取代时, T-O相变温度同样下降, 尽管随组成下降略缓, 相反的是O-R相变温度升高, 8%的Zr4+取代就能将R相移到室温; Sb5+的取代同样能够提高O-R相变温度, 9%的Sb取代将O-R相变温度提升到室温; Ta取代会引起居里温度的下降, 并降低T-O相变温度^{[4, 6]}。从这些离子取代对O-R的影响规律上看, O-R相变的决定因素不仅仅是由B位离子半径引起的化学应力, 化学键的强弱也可能是影响因素。总之, 通过MPB和PPT相界组成的优化, 在0.90(Na_0.5K_0.5)NbO_3-xBaZrO₃-(0.10-x)(Bi_0.5Li_0.5)TiO₃体系中, 当x=0.7~0.8时, d₃₃ =230~265 pC/N, k_p=40.6%~41.9%。当组成为0.92(Na_0.5K_0.5)NbO₃-0.06BaZrO₃-0.02(Bi_0.5K_0.5)TiO₃-0.25wt%MnO₂时, d₃₃=420 pC/N, k_p=56%, T_c=243℃^[7-9], 其室温压电性能与PZT-4陶瓷接近, 但是其温度稳定性和长期工作的可靠性还有待进一步研究和考验, 因此, 关于“垂直相界的研究”将是今后的重要研究内容之一^[10]。 　　不同离子取代时KNN中不同相变调控规律, 其机理仍需要进一步探讨。对复杂的KNN固溶体中相界和相变的系统实验和理论研究有可能是实现无铅压电陶瓷实际应用的最有希望的突破口。 2 高性能陶瓷储能介质的研究 　　储能电容器具有储能密度高、充放电速度快、抗循环老化、高温和高压等极端环境下性能稳定等优点, 在电动汽车、功率电子器件、脉冲功率电源、高能量密度武器、新能源及智能电网系统等基础科研和工程应用领域有着广阔的应用前景[11]。 　　美国EEStor公司在静电介质超级电容器方面申请了多项专利^[12], 如“采用陶瓷介质和集成电路技术的电能存储单元(EESU)取代电化学电池”的专利技术在学术界和产业界产生了强烈反响, 对纯电动汽车来说, 无疑是一个重大突破, 但相关的技术细节、验证和实施还需要大量的研究工作。 　　章启明等^[13]在有机介质电容器中实现了高密度储能的新途径(>17 J/cm³), 引起人们对介质超级电容器储能系统的广泛重视。最近, 刘芸等^[14]报道在(Nb/In)共掺杂的金红石TiO₂陶瓷中形成缺陷偶极子团簇, 在宽温区获得巨介电常数(>104)的同时具有较小的介质损耗(<0.05)。 　　当前, 正在开展的研究工作还有陶瓷晶粒包裹玻璃层、在玻璃之中析出极性区域以及BaTiO₃表面包覆一层Al(OH)x离子介质层可能形成电化学赝电容等方法^[15], 这种通过引入离子导电性晶界使电化学赝电容与静电电容共存的概念, 为陶瓷储能电容器研究开启了新的思路。同时, 在双电层电容器中也在尝试引入电介质层来提高其工作电压。各种技术优势的相互渗透和交融大大激发了新概念、新机理电容器的研究, 无疑会促进电容器储能技术和应用的发展。 3 巨电卡效应 　　电卡效应是指在极性材料中因外电场的改变导致极化状态发生改变而产生的绝热温度或等温熵的变化。上个世纪30年代就有电卡效应的报道, 只是由于陶瓷材料的工作场强低, 得到绝热温度的变化都小于1℃。近年来, 相关研究取得飞速发展, 为此, 本专辑特邀鲁圣国教授撰写相关综述论文, 以飨读者。 　　2006年, Mischenko等报道了在溶胶-凝胶法制备的Pb(Zr_0.95Ti_0.05)O₃反铁电薄膜的电卡效应, 薄膜厚度为350 nm, 工作电场为48 MV/m, 得到了绝热温变为12℃, 熵变ΔS=8 J/(kg?K)^[16]。随后, 章启明等^[17]在铁电共聚物(P(VDF-TrFE, 68/32 mol%)中获得大的铁电-顺电相变热为2.1×10⁴ J/kg, 熵变ΔS=56.0 J/(kg?K), 为巨电卡效应和新材料研究开启了新的大门。 　　鲁圣国等^[18]在PLZT8/65/35薄膜中观察到绝热温变达40 K, 等温熵变达50 J/(kg?K)的现象。最近, 樊慧卿等^[19]在Pb_0.8Ba_0.2ZrO₃薄膜中, 也发现存在室温巨电卡效应, 在工作电场为598 kV/cm时, 电卡效应的最佳值为ΔT= 45.3 K,ΔS = 46.9 J/(kg?K)。 　　上述这些研究结果预示着一种新的制冷技术实现变革的可能性, 利用固态电卡制冷原理取代传统卡诺制冷压缩机的超小体积、高效节能和环保无制冷剂的新一代冰箱、空调等将成为功能陶瓷研究新热点。     

陶瓷电介质储能材料研究进展EI北大核心CSCD

为了更好地推动高储能密度和高效率无铅陶瓷介质电容器的研究与发展,本文综合介绍了陶瓷电介质储能材料的储能原理及分类,比较分析了近年来线性电介质、铁电体、弛豫铁电体和反铁电体储能材料的研究进展,主要研究体系和性能优劣。总结了陶瓷储能材料目前面临的挑战以及改善其储能性能的策略,展望了其未来在5G通信、新能源汽车、消费电子等工业应用中的发展及小型化、高耐电压性、高可靠性的技术发展趋势。     

Piezoelectric ceramics with high dielectric constants for ultrasonic medical transducers

Complex system ceramics Pb(Sc(1/2)Nb(1/2))O3-Pb(Mg(1/3)Nb(2/3))O3-Pb(Ni(1/2)Nb(1/2))O3-(Pb0.965,Sr0.035) (Zr,Ti)O3 (PSN-PMN-PNN-PSZT abbreviated PSMNZT) have been synthesized by the conventional technique, and dielectric and piezoelectric properties of the ceramics have been investigated for ultrasonic medical transducers. High capacitances of the transducers are desired in order to match the electrical impedance between the transducers and the coaxial cable in array probes. Although piezoelectric ceramics that have high dielectric constants (epsilon33t/epsilon0 > 5000, k'33 < 70%) are produced in many foundries, the dielectric constants are insufficient. However, we have reported that low molecular mass B-site ions in the lead-perovskite structures are important in realizing better dielectric and piezoelectric properties. We focused on the complex system ceramics PSMNZT that consists of light B-site elements. The maximum dielectric constant, epsilon33T/epsilon0 = 7, 200, was confirmed in the ceramics, where k'33 = 69%, d33 = 940 pC/N, and T(c) = 135 degrees C were obtained. Moreover, pulse-echo characteristics were simulated using the Mason model. The PSMNZT ceramic probe showed echo amplitude about 5.5 dB higher than that of the conventional PZT ceramic probe (PZT-5H type). In this paper, the electrical properties of the PSMNZT ceramics and the simulation results for pulse-echo characteristics of the phased-array probes are introduced.     

Carbons and Electrolytes for Advanced Supercapacitors

Electrical energy storage (EES) is one of the most critical areas of technological research around the world. Storing and efficiently using electricity generated by intermittent sources and the transition of our transportation fleet to electric drive depend fundamentally on the development of EES systems with high energy and power densities. Supercapacitors are promising devices for highly efficient energy storage and power management, yet they still suffer from moderate energy densities compared to batteries. To establish a detailed understanding of the science and technology of carbon/carbon supercapacitors, this review discusses the basic principles of the electrical double‐layer (EDL), especially regarding the correlation between ion size/ion solvation and the pore size of porous carbon electrodes. We summarize the key aspects of various carbon materials synthesized for use in supercapacitors. With the objective of improving the energy density, the last two sections are dedicated to strategies to increase the capacitance by either introducing pseudocapacitive materials or by using novel electrolytes that allow to increasing the cell voltage. In particular, advances in ionic liquids, but also in the field of organic electrolytes, are discussed and electrode mass balancing is expanded because of its importance to create higher performance asymmetric electrochemical capacitors.     

Multilayer PZT 95/5 Antiferroelectric Film Energy Storage Devices with Giant Power Density

A new type of energy storage devices utilizing multilayer Pb(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ films is studied experimentally and numerically. To release the stored energy, the multilayer ferroelectric structures are subjected to adiabatic compression perpendicular to the polarization direction. Obtained results indicate that electrical interference between layers (10–120 layers) during stress wave transit through the structures has an effect on the generated current waveforms, but no impact on the released electric charge. The multilayer films undergo a pressure‐induced phase transition to antiferroelectric phase at 1.7 GPa adiabatic compression and become completely depolarized, releasing surface screening charge with density equal to their remnant polarization. An energy density of 3 J cm^?3 is successfully achieved with giant power density on the order of 2 MW cm^?3, which is four orders of magnitude higher than that of any other type of energy storage device. The outputs of multilayer structures can be precisely controlled by the parameters of the ferroelectric layer and the number of layers. Multilayer film modules with a volume of 0.7 cm³ are capable of producing 2.4 kA current, not achievable in electrochemical capacitors or batteries, which will greatly enhance the miniaturization and integration requirements for emerging high‐power applications.     

Alkali-free glass as a high energy density dielectric material

One of the greatest challenges in the development of new high energy density materials is to increase dielectric permittivity while maintaining high breakdown strength. The dielectric breakdown behavior of an alkali-free barium boroaluminosilicate glass is shown to have remarkably high DC dielectric breakdown strength (12 MV/cm) and reasonably high permittivity (~ 6), equating to energy densities in excess of 35 J/cm³. This behavior is attributed to highly polarizable Ba ions enhancing the real part of complex permittivity, the low loss due to the alkali-free composition, and the substantially defect-free quality of the glass and its surfaces. To our knowledge, this is the highest breakdown strength reported for a bulk glass, and rivals the breakdown strength more typically observed in pristine thin films of SiO₂. These findings indicate that alkali-free multicomponent glasses may be strong candidates for next-generation high energy density storage capacitors for portable or pulsed power applications.     

Layer-Controlled Perovskite 2D Nanosheet Interlayer for the Energy Storage Performance of Nanocomposites

Polymer-based nanocomposites are desirable materials for next-generation dielectric capacitors. 2D dielectric nanosheets have received significant attention as a filler. However, randomly spreading the 2D filler causes residual stresses and agglomerated defect sites in the polymer matrix, which leads to the growth of an electric tree, resulting in a more premature breakdown than expected. Therefore, realizing a well-aligned 2D nanosheet layer with a small amount is a key challenge; it can inhibit the growth of conduction paths without degrading the performance of the material. Here, an ultrathin Sr_1.8Bi_0.2Nb₃O₁₀ (SBNO) nanosheet filler is added as a layer into poly(vinylidene fluoride) (PVDF) films via the Langmuir–Blodgett method. The structural properties, breakdown strength, and energy storage capacity of a PVDF and multilayer PVDF/SBNO/PVDF composites as a function of the thickness-controlled SBNO layer are examined. The seven-layered (only 14 nm) SBNO nanosheets thin film can sufficiently prevent the electrical path in the PVDF/SBNO/PVDF composite and shows a high energy density of 12.8 J cm⁻³ at 508 MV m⁻¹, which is significantly higher than that of the bare PVDF film (9.2 J cm⁻³ at 439 MV m⁻¹). At present, this composite has the highest energy density among the polymer-based nanocomposites under the filler of thin thickness.     

Structure and electrical properties of (111)-oriented Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 thin film for ultra-high-frequency transducer applications

Ternary lead magnesium niobate-lead zirconate titanate system 0.4Pb(Mg(1/3)Nb(2/3))O(3)-0.25PbZrO(3)-0.35PbTiO(3) (40PMN-25PZ-35PT) thin film with a thickness of 1.5 μm was grown on Pt(111)/Ti/SiO(2)/Si substrate via chemical solution deposition. X-ray diffraction and transmission electron microscopy results suggested the film obtained was highly (111)-oriented. The remanent polarization and coercive electric field of the film were found to be 25.5 μC/cm(2) and 51 kV/cm, respectively. In addition, at 1 kHz, the dielectric constant was measured to be 1960 and the dielectric loss 0.036. The film was observed to undergo a diffuse ferroelectric-to-paraelectric phase transition at around 209°C. The leakage current appeared to depend on the voltage polarity. If the Au electrode was biased positively, the leakage current was dominated by the Schottky emission mechanism. When the Pt electrode was biased positively, the conduction current curve showed an ohmic behavior at a low electric field and space-charge-limited current characteristics at a high electric field.     

Harmonic analysis of the polarization response in Pb(Mg(1/3 )Nb(2/3))O(3)-based ceramics-A study in aging

The polarization response of a ferroelectric ceramic displays nonlinear behavior at high applied fields due to saturation effects. Weak-field dielectric aging imposes additional nonlinearity on the hysteresis loops of these materials. Harmonic analysis using a discrete Fourier transform (DFT) permitted an observation of the change in the polarization frequency spectrum as Pb(Mg(1/3)Nb(2/3))O (3)-based relaxor ceramics aged. It also facilitated the calculation of ac current, power, and "internal bias field". The results show that particular harmonics in the polarization signal are sensitive indications of aging behavior. The average power dissipated at weak ac fields was found to decrease with aging time; and the power dissipated at strong fields tended to increase.     

Intertwined Nanocarbon and Manganese Oxide Hybrid Foam for High‐Energy Supercapacitors

Rapid charging and discharging supercapacitors are promising alternative energy storage systems for applications such as portable electronics and electric vehicles. Integration of pseudocapacitive metal oxides with single‐structured materials has received a lot of attention recently due to their superior electrochemical performance. In order to realize high energy‐density supercapacitors, a simple and scalable method is developed to fabricate a graphene/MWNT/MnO₂ nanowire (GMM) hybrid nanostructured foam, via a two‐step process. The 3D few‐layer graphene/MWNT (GM) architecture is grown on foamed metal foils (nickel foam) via ambient pressure chemical vapor deposition. Hydrothermally synthesized α‐MnO₂ nanowires are conformally coated onto the GM foam by a simple bath deposition. The as‐prepared hierarchical GMM foam yields a monographical graphene foam conformally covered with an intertwined, densely packed CNT/MnO₂ nanowire nanocomposite network. Symmetrical electrochemical capacitors (ECs) based on GMM foam electrodes show an extended operational voltage window of 1.6 V in aqueous electrolyte. A superior energy density of 391.7 Wh kg^?1 is obtained for the supercapacitor based on the GMM foam, which is much higher than ECs based on GM foam only (39.72 Wh kg^?1). A high specific capacitance (1108.79 F g^?1) and power density (799.84 kW kg^?1) are also achieved. Moreover, the great capacitance retention (97.94%) after 13 000 charge–discharge cycles and high current handability demonstrate the high stability of the electrodes of the supercapacitor. These excellent performances enable the innovative 3D hierarchical GMM foam to serve as EC electrodes, resulting in energy‐storage devices with high stability and power density in neutral aqueous electrolyte.     

Enhanced dielectric properties and energy storage density of surface engineered BCZT/PVDF-HFP nanodielectrics

Polymer nanocomposites have proved to be promising energy storage devices for modern power electronic systems. In this work we have studied the dielectric properties and dielectric energy storage densities of 0–3 type BCZT/PVDF-HFP polymer nanocomposites with different filler volume concentrations. BCZT nanopowder was synthesized by solgel method through citrate precursor method. The structural and morphological features of the BCZT nanopowder were examined by X-ray diffraction and transmission electron microscopy. For better polymer ceramic interface coupling, BCZT was surface functionalized with extended aromatic ligand, naphthyl phosphate (NPh). The surface functionalization was validated and quantified by thermogravimetric analysis and X-ray photoelectron spectroscopy. The dielectric constant of surface passivated BCZT nanoparticles was estimated to be ~?155 using slurry technique, while the dielectric permittivity of pristine BCZT nanopowder could not be assessed due to high innate surface conductivity. BCZT/PVDF-HFP polymer nanocomposite thin films were fabricated using solution casting technique. The dispersion quality of the ceramic fillers in the polymer matrix was examined by scanning electron microscopy. Due to better polymer ceramic interface, At 5 vol% filler concentration, NPh modified nanoBCZT/PVDF-HFP films showed enhanced dielectric breakdown strength and energy storage density than untreated nanoBCZT/PVDF-HFP and even pure polymer films. Maximum energy storage density of 8.5 J cm^?3 was obtained at an optimum filler concentration of 10 vol% for surface functionalized BCZT/PVDF-HFP composite films of 10 μm thickness.     

Advanced Materials for Energy Storage

Popularization of portable electronics and electric vehicles worldwide stimulates the development of energy storage devices, such as batteries and supercapacitors, toward higher power density and energy density, which significantly depends upon the advancement of new materials used in these devices. Moreover, energy storage materials play a key role in efficient, clean, and versatile use of energy, and are crucial for the exploitation of renewable energy. Therefore, energy storage materials cover a wide range of materials and have been receiving intensive attention from research and development to industrialization. In this Review, firstly a general introduction is given to several typical energy storage systems, including thermal, mechanical, electromagnetic, hydrogen, and electrochemical energy storage. Then the current status of high‐performance hydrogen storage materials for on‐board applications and electrochemical energy storage materials for lithium‐ion batteries and supercapacitors is introduced in detail. The strategies for developing these advanced energy storage materials, including nanostructuring, nano‐/microcombination, hybridization, pore‐structure control, configuration design, surface modification, and composition optimization, are discussed. Finally, the future trends and prospects in the development of advanced energy storage materials are highlighted.     

改性(Sr,Ca)TiO3基储能陶瓷介电及MLCC性能研究

工业级脉冲储能多层瓷介电容器(MLCC)是现阶段国内研制和生产电子启动装置的重要元器件, 针对国内主要有机薄膜电容器尺寸大、寿命短、可靠性较低的不足, 本研究采用传统固相反应法, 制备了SrTiO₃和CaTiO₃基的脉冲储能介质陶瓷材料, 研究了微量助烧剂掺杂, 以及Sr²⁺/Ca²⁺相互掺杂对陶瓷材料的介电性能的影响, 并进一步制备和研究了以(Sr,Ca)TiO₃为基体MLCC性能。实验结果表明: 通过加入质量分数1.0%的助烧剂, 引入微量Bi³⁺ 可取代Sr²⁺, 提高了SrTiO₃材料的介电常数, 而Bi³⁺对CaTiO₃基材料的介电性能无明显影响; Mn元素有效抑制高温烧结中Ti⁴⁺的还原, 降低介电损耗; 加入助烧剂有效降低瓷粉的烧结温度, 提高材料的致密性。(Sr_xCa_1-x)TiO₃体系的MLCC可保持较高的介电常数和较低的介电损耗, 当 x=0.4 时, 其介电损耗tanδ=1.8×10^-4, 击穿强度为59.38 V/μm, 高低温放电电流变化率为±7%, 放电稳定, 在常温和高温(125 ℃)下经1000次循环充放电实验均未失效, 是一种在不同电场强度下具有相对较优的容量稳定性以及较高可靠性的脉冲特性(Sr,Ca)TiO₃基电容器陶瓷介质材料。     

Effect of microwave annealing temperatures on lead zirconate titanate thin films

Lead zirconate titanate (Pb(1.1)(Zr(0.52)Ti(0.48))O(3)) thin films of thickness 260?nm on Pt/Ti/SiO(2)/Si substrates were densified by 2.45?GHz microwave annealing. The PZT thin films were annealed at various annealing temperatures from 400 to 700?°C for 30?min. X-ray diffraction showed that the pyrochlore phase was transformed to the perovskite phase at 450?°C and the film was fully crystallized. The secondary (again pyrochlore) phase was observed in the PZT thin films, which were annealed above 550?°C. The surface morphologies were changed above 550?°C of the PZT thin films due to the secondary phase. Higher dielectric constant (ε(r)) and lower dielectric loss coercive field (E(c)) were achieved for the 450?°C film than for the other annealed films.