溶胶-凝胶法合成Ba0.6Sr0.4TiO3/MgO及介电性能研究

采用溶胶-凝胶法合成了Ba_(0.6)Sr_(0.4)TiO_3/MgO复合粉体,研究了烧结温度和合成工艺对陶瓷样品介电性能的影响。研究结果表明,经650℃热处理即可得到颗粒细小均匀的超细Ba_(0.6)Sr_(0.4)TiO_3/MgO粉体,平均粒径在200 nm左右。烧结温度对陶瓷样品的介电生能有明显的影响,1300℃烧结的陶瓷样品具有优良的性能。与二步合成工艺相比,一步合成工艺制备的陶瓷样品具有更好的介(?)性能。     

钛酸锶钡(Ba_(0.7)Sr_(0.3)TiO_3)厚膜陶瓷的大电卡效应和储能密度

采用固相反应法制备了钛酸锶钡(Ba_(0.7)Sr_(0.3)TiO_33)精细粉体,通过流延法制备出厚度约55μm的厚膜陶瓷。利用X射线衍射和扫描电子显微镜分析了样品的物相组成和微观形貌。利用阻抗分析仪和铁电电滞回线测试仪测量了厚膜陶瓷样品的介电性能和铁电性能。根据Maxwell关系估算了电卡效应,并根据电滞回线计算了储能密度和储能效率。结果表明:钛酸锶钡(Ba_(0.7)Sr_(0.3)TiO_33)厚膜在330 K(57℃)Curie温度附近、30 MV/m电场下绝热温变达到3.43 K,同时在30 MV/m电场时储能密度达到1.43 J/cm3,显示出良好的电卡性能和储能特性。     

基于水热合成粉末的Ba0.6Sr0.4TiO3厚膜陶瓷及其大电卡效应

通过两步水热法制备了纳米钛酸锶钡(Ba_(0.6)Sr_(0.4)TiO_3)粉体,利用流延成型法得到钛酸锶钡厚膜生坯,通过叠压、静水压、排胶及烧结后得到厚膜陶瓷。使用X射线衍射仪、扫描电子显微镜、精密阻抗分析仪和铁电测试平台对其晶体结构、形貌、介电性能以及铁电性能进行了表征。结果表明:两步水热法得到的钛酸锶钡纳米粉体形貌为均匀的准立方体,平均颗粒尺寸为50 nm。烧结成厚膜陶瓷后平均晶粒尺寸达到2.2mm。通过电滞回线分析得到不同温度和电场下的极化强度,利用Maxwell关系得到电卡效应的绝热温变在温度253 K以及电场5 MV/m下达到0.62 K。     

微波介电陶瓷Ba_(1.5)Sr_(0.5)La_2Ti_2TaO_(12)的合成及介电特性研究

微波介电陶瓷在通讯器件中制备材料,其材料的性能提升与制备成为研究的重点,吸引了越来越多的研究人员。其中对以钽酸盐为代表的介电陶瓷的应用越来越多,为此,制备合成了微波介电陶瓷Ba_(1.5)Sr_(0.5)La_2Ti_2TaO_(12)。采用X射线衍射分析进行了结构分析、并用LCR测量仪对其介电性能进行了测试。结果表明:Ba_(1.5)Sr_(0.5)La_2Ti_2TaO_(12)结构为六方层状类钙钛矿,晶胞常数为:a=b=5.712,c=27.934,V=789.27~3,Z=3,具有优异的介电性能。介电常数为44.38,介电损耗为0.0013。该陶瓷体具有优异的介电性能。     

微波介电陶瓷Ba_(1.8)Sr_(0.2)La_2Ti_2NbO_(12)的合成及介电特性研究

制备合成了微波介电陶瓷Ba_(1.8)Sr_(0.2)La_2Ti_2Nb O_(12)。采用X射线衍射分析进行了结构分析、并用LCR测量仪对其介电性能进行了测试。结果表明:Ba_(1.8)Sr_(0.2)La_2Ti_2Nb O_(12)结构为六方层状类钙钛矿,晶胞常数为:a=b=5.691 7),c=27.820 7),V=780.28 7)~3,Z=3,具有优异的介电性能。介电常数为46.4,介电损耗为0.00083。     

钛酸锶钡陶瓷的介电性及其在静电净油中应用

为进一步提高静电净油技术中的非均匀电场梯度,在具有"城垛"型结构净油装置中引入钛酸锶钡电介质瓷粉,采用固相法制得微结构、电性能适于净油的Ba_(0.7)Sr_(0.3)TiO_3陶瓷,在此基础上研究了电场强度和净化时间对静电净油效果的影响。结果表明:Ba_(0.7)Sr_(0.3)TiO_3瓷粉为平均粒径为40μm,在30～40℃范围内介电常数为9000～11000,适于用作静电净油的高介无机电介质材料。Ba_(0.7)Sr_(0.3)TiO_3瓷粉的引入改善了净油环境和非均匀电场梯度,从而增强了装置对油液中Fe_2O_3的吸附,除杂率最高可达91.08%。     

CaSnO_3掺杂BST基介电陶瓷介电性能的研究

采用传统固相法制备了CaSnO_3掺杂(Ba_(0.71)Sr_(0.29))TiO_3(BST)介电陶瓷。研究了CaSnO_3掺杂量对BST电容器介电陶瓷介电性能、物相组成和微观结构的影响。结果表明:随着Ca SnO_3掺杂量的增加,BST陶瓷的相对介电常数(εr)先减小后增大再又减小,介质损耗(tanδ)先减小然后增大,CaSnO_3掺杂后的BST陶瓷仍为钙钛矿结构。当CaSnO_3掺杂量为质量分数6.0%时,BST陶瓷的综合介电性能最好:εr为4963,tanδ为0.0069,ΔC/C为19.69%～-26.18%,容温特性符合Y5V特性。     

Bi_4Ti_3O_(12)掺杂(Ba,Sr)TiO_3基电容器陶瓷介电性能研究

采用传统固相法制备了Bi_4Ti_3O_(12)掺杂(Ba_(0.71),Sr_(0.29))TiO_3(BST)陶瓷。研究了Bi_4Ti_3O_(12)掺杂量对BST电容器陶瓷介电性能、物相组成和微观结构的影响。结果表明:随着Bi_4Ti_3O_(12)掺杂的增加,BST陶瓷的相对介电常数逐渐减小,介电损耗先减小然后增大,Bi_4Ti_3O_(12)掺杂后的BST陶瓷仍为钙钛矿结构。当Bi_4Ti_3O_(12)掺杂量为1.6 wt%时,BST陶瓷的综合介电性能最好,εr为3744,tanδ为0.0068,ΔC/C为+1.70%,-44.61%,容温特性符合Y5V特性。     

PbO-SiO2玻璃对Ba0.4Sr0.6TiO3陶瓷致密度和介电性能的影响

为了制备耐高压、高储能密度陶瓷电容器,研究了不同PbO-SiO2(PS)玻璃添加量对Ba0.4Sr0.6TiO3陶瓷致密度和介电性能的影响。结果表明:PS玻璃能有效降低Ba0.4Sr0.6TiO3陶瓷的烧结温度,细化晶粒,提高样品的致密度。添加适量PS玻璃改善了Ba0.4Sr0.6TiO3陶瓷的介电性能。添加质量分数为1%PS玻璃的Ba0.4Sr0.6TiO3陶瓷在1100℃烧结致密,相对密度达到98.3%,平均击穿场强达到15.4kV/mm,相对于纯Ba0.4Sr0.6TiO3陶瓷的提高了1.5倍,1kHz的室温相对介电常数达到1179,介电损耗为6×10-4。     

Tm~(3+)和Dy~(3+)共掺氟氧铝硼硅酸盐玻璃微晶化及白光发射性能

采用高温熔融-淬火/热处理方法在空气气氛中制备了Tm_2O_3和Dy_2O_3共掺氟氧铝硼硅酸盐玻璃及透明微晶玻璃。用转靶多晶X射线衍射仪、荧光分光光度计和热分析仪对玻璃样品进行了表征。结果表明:样品在640～660℃热处理4h和在640℃热处理4～16h可制得透明的含Ba_2LaF_7纳米晶玻璃。增大Tm-Dy共掺浓度并降低La_2O_3浓度时,Ba_2LaF_7析晶倾向降低。此外,热处理析出Ba_2LaF_7微晶相后,样品的Tm_2O_3和Dy_2O_3共掺浓度淬灭点由1%(摩尔分数,下同)提高到了2%。掺杂不同浓度Tm_2O_3和Dy_2O_3时,白光发光色度保持不变。     

Microstructures and dielectric properties of spark plasma sintered Ba0.4Sr0.6TiO3/CaCu3Ti4O12 composite ceramics

(1 − x)Ba_0.4Sr_0.6TiO₃/xCaCu₃Ti₄O₁₂ composite ceramics were prepared by spark plasma sintering. Sintering behavior, microstructures and dielectric properties of the composite ceramics were investigated by XRD, SEM, EDS and dielectric spectrometer. Dense composite ceramics consisting of Ba_0.4Sr_0.6TiO₃ phase and CaCu₃Ti₄O₁₂ phase were prepared at 800 °C for 0 min. The dielectric loss of the composite ceramic decreased with increasing amount of Ba_0.4Sr_0.6TiO₃, and the high dielectric constant were retained. Moreover, the better temperature stability of dielectric constant was obtained. These improvements of dielectric characteristics have great scientific significance for potential application.     

Reduced leakage current,enhanced energy storage and dielectric properties in (Ce,Mn)-codoped Ba0.6Sr0.4TiO3 thin film

Ba_0.6Sr_0.4TiO₃, Ce-doped Ba_0.6Sr_0.4TiO₃, Mn-doped Ba_0.6Sr_0.4TiO₃, (Ce,Mn) co-doped Ba_0.6Sr_0.4TiO₃ (abbreviated as BST, BSTCe, BSTMn, BSTCeMn) thin films were deposited on LaNiO₃(LNO)/Si substrates. The effects of ion doping on the microstructure and electrical properties of BST-based thin film have been researched and discussed. The X-ray diffraction pattern shows that each sample has pure perovskite phase structure with high (l00) peaks. The microstructure of each film is quite dense with uniform size. Compared with pure BST, improved insulating properties can be found in ion-doped BST thin films. For all the films, Ohmic conduction, space charge limited conduction and interface-limited Fowler-Nordheim tunneling should be the main conduction mechanisms within different electric field regions. For the case of BSTCeMn thin film, it possesses enhanced energy storage performance with a recoverable energy storage density (18.01?J/cm³) and a energy storage efficiency (75.1%) under 2000?kV/cm. This can be closely related to the small remanent polarization value (P_r=?1.89 μC/cm²), large maximum polarization value (P_max=?28.08?μC/cm²) as well as big maximum electric field (2000?kV/cm). Also, it exhibits a large dielectric constant of 405 and a small dissipation factor of 0.075 at 500?kHz.     

Dielectric Properties and Low‐Temperature Sintering of the Ba0.6Sr0.4TiO3 Ceramics with B2O3/CuO Additions

The sintering behaviors and dielectric properties of Ba_0.6Sr_0.4TiO₃ ceramics were investigated as a function of B₂O₃ and CuO content. The addition of both B₂O₃ and CuO reduced the sintering temperature of Ba_0.6Sr_0.4TiO₃ about 500°C. It was suggested that a liquid phase BaCu(B₂O₅) was formed and assisted the densification of Ba_0.6Sr_0.4TiO₃ ceramics. Ba_0.6Sr_0.4TiO₃ ceramics co‐doped with 3.0 mol% B₂O₃, and 2.0 mol% CuO, sintered at 950°C for 5 h, had a dense microstructure and showed good microwave dielectric properties of a moderate dielectric constant (ε = 1048), low dielectric loss (0.0090) and high tunability (42.2%) at dc electric field of 30 kV/cm.     

Microstructure and dielectric properties of Ba0.6Sr0.4TiO3-MgAl2O4 composite ceramics

(1 − x)Ba_0.6Sr_0.4TiO₃-xMgAl₂O₄(x = 25, 30, 35 and 40 wt%) composite ceramics were prepared by conventional solid-state reaction method. The microstructures, dielectric properties and tunability of the composites have been investigated. The XRD patterns analysis reveals two crystalline phases, a cubic perovskite structure Ba_0.6Sr_0.4TiO₃ (BST) and a spinel structure MgAl₂O₄ (MA). SEM observations show that the BST grains slightly dwindle and agglomerate with increasing amounts of MA. A dielectric peak with very strong frequency dispersion is observed at higher MA content, and the Curie temperature shifts to a higher temperature with increasing MA content. The ceramic sample with 30 wt% MA has the optimized properties: the dielectric constant is 1503, the dielectric loss is 0.003 at 10 kHz and 25 °C, the tunability is 23.63% under a dc electric field of 1.0 kV/mm, which is suitable for ferroelectric phase shifter.     

Ba0.4Sr0.6TiO3/MgO Composites with Enhanced Energy Storage Density and Low Dielectric Loss for Solid-State Pulse-Forming Line

(100−x) wt% Ba_0.4Sr_0.6TiO₃−x wt% MgO composites (10≤x≤30) were prepared using Ba_0.4Sr_0.6TiO₃ powder and nanosized MgO powder (∼60 nm) by a solid-state reaction. The energy storage density and dielectric loss were investigated for the purpose of a potential application in solid-state pulse-forming line. The results show that Ba_0.4Sr_0.6TiO₃/MgO composites exhibit a notably enhanced energy density and low dielectric loss, compared with pure Ba_0.4Sr_0.6TiO₃. The enhancement of the energy density is attributed to the notable increase in breakdown strength of the composites and the improvement of dielectric constant stability with regard to electric field. In the case of x=30, the samples exhibited a breakdown strength of 33.1 kV/mm, an energy density of 1.14 J/cm³, a moderate dielectric constant of 270, and a low dielectric loss of 4 × 10⁻⁴.     

High Tunability of Nonepitaxially Grown Ba0.6Sr0.4TiO3 Thin Films Prepared by Plasma‐Assisted Pulsed Laser Deposition

Nonepitaxially grown Ba_0.6Sr_0.4TiO₃ (NE‐BSTO) thin film with tunability of 65.4% and low leakage current was obtained on Ir electrode by oxygen plasma‐assisted pulsed laser deposition (PLD), and epitaxially grown Ba_0.6Sr_0.4TiO₃ (E‐BSTO) thin film with tunability of 32.5% was obtained by PLD without plasma assistance. Results indicate that the NE‐BSTO film possessed higher oxygen content, lower tetragonal distortion, and low stress, all of which contributed to its excellent dielectric properties. This work demonstrates that NE‐BSTO thin films are well suited for room temperature tunable microwave device applications.     

Raman and dielectric investigation of (Ba0.9−xSrxCa0.1)(Ti0.8Zr0.2)O3 ferroelectric ceramics

Solid solutions of (Ba_0.9−xSr_xCa_0.1)(Ti_0.8Zr_0.2)O₃ (BSCTZ) (0.1≤x≤0.4) were prepared using the conventional solid state reaction method. The effects of the substitution content on the crystallographic structure, phase transition and dielectric properties of the samples were investigated by dielectric and Raman spectroscopy over a wide temperature range from 100 to 500 K. All the samples were noted to undergo a diffuse phase transition from the tetragonal to the cubic phase and to exhibit a relaxor ferroelectric behavior.     

Thermal annealing effects on the energy storage properties of BST ceramics

Thermal annealing treatments with different atmospheres (air, oxygen, and reducing atmospheres, respectively) were employed for the conventionally sintered (Ba_0.4Sr_0.6)TiO₃ (BST) ceramics. The effect of thermal annealing on the energy storage properties of BST ceramics was investigated, where oxygen vacancies played an important role. The dielectric loss, bulk resistivity and dielectric breakdown strength (BDS) were found to be sensitive to the annealing process, leading to the different energy densities in the range of 0.30‐0.80 J/cm³. Temperature‐dependent dielectric measurement and thermally stimulated depolarization current analysis were conducted to understand the impacts of oxygen vacancies on the macroscopic properties, which were found to be closely associated with the annealing conditions.     

Achieving high breakdown strength and figure of merit of Ba0.6Sr0.4TiO3 films through coating a Y3Fe5O12 layer

Low tunability and figure of merit significantly limited the application of Ba_0.6Sr_0.4TiO₃ (BST) ferroelectric film, which originates from the low electric breakdown strength and high dielectric loss of BST layer. Garnet structured Y₃Fe₅O₁₂ (YIG) exhibits the merits of good microwave dielectric property and a much high resistivity, which are helpful for enhancing the breakdown strength and suppressing the dielectric loss. In this work, Y₃Fe₅O₁₂/Ba_0.6Sr_0.4TiO₃ (YIG/BST) composite films were fabricated via chemical solution deposition method. The composite films exhibited a low dielectric loss (0.006) and an almost frequency independent dielectric constant in a frequency range from 10 kHz to 1 MHz. The electric breakdown strength was significantly enhanced from less than 400 kV/cm to around 800 kV/cm through coating a YIG layer, causing an excellent tunability of 72.84% and an ultra-high figure of merit (FOM=118) at 800 kV/cm in YIG/BST film. It is physically clarified that the conduction loss plays an important role in BST film while the intrinsic loss is the dominate factor for the YIG/BST composite films.     

B-site modification of (Ba0.6Sr0.4)TiO3 ceramics with enhanced diffuse phase transition behavior

(Ba_0.6Sr_0.4)TiO₃ (BST) ceramics modified with both Zr and Mn were synthesized via a traditional solid state reaction route. Pure perovskite structure and dense morphology were obtained for all specimens. An enhanced diffuse phase transition (DPT) behavior induced by Mn substitution was detected. We suggest that such enhanced DPT behavior was beneficial for BST practical applications due to the improved dielectric thermal stability while maintaining good dielectric performance. The impact of Mn concentration on the microstructure, dielectric properties, and DPT diffuseness was investigated.