Dielectric tunable properties of BaTi<Subscript>4</Subscript>O<Subscript>9</Subscript>-doped Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>TiO<Subscript>3</Subscript> microwave composite ceramics

BaTi₄O₉-doped Ba_0.6Sr_0.4TiO₃ (BST) composite ceramics were prepared by the conventional solid-state reaction and their structure, dielectric nonlinear characteristics and microwave dielectric properties were investigated. The secondary phase of the orthorhombic structure Ba₄Ti₁₃O₃₀ is formed among BST composite ceramics with the increase of BaTi₄O₉. At the same time, a duplex or bimodal grains size distribution shows fine grains in a coarse grain matrix. The degree of frequency dispersion of dielectric permittivity below T _m is increased initially and then decreased with respect to BaTi₄O₉. As the BaTi₄O₉ content increases, the tunability of composite ceramics decreases, while the Q value increases. Interestingly, 70 wt% BaTi₄O₉-doped BST has a tunability ∼4.0% (under 30 kV/cm biasing) versus a permittivity ∼68 and quality factor ∼134.1 (at ∼3.2 GHz). Supported by the Ministry of Science and Technology of China through 973-project (Grant No. 2009CB623302), the Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (Grant No.707024), Shanghai Committee of Science and Technology (Grant No. 07DZ22302), and Shanghai Foundation Project under 06JC14070     

中温烧结0.6Mg_4Nb_2O_9-0.4SrTiO_3复相陶瓷

采用传统固态反应方法制备0.6Mg4Nb2O9-0.4SrTiO3复合陶瓷。研究LiF掺杂对其烧结特性、相结构和微观形貌的的影响。通过X射线衍射(XRD)和扫面电镜(SEM)观察样品的相组成和显微结构。实验结果表明:1.5 wt%LiF添加,可将Mg4Nb2O9/SrTiO3陶瓷的致密化烧结温度从1300℃降至1100℃;XRD表明除主相Mg4Nb2O9、SrTiO3外,还有少量新相Sr(Ti1-xNbx)O3+δ生成。     

Microstructure and dielectric properties of BaTi_4 O_9 (f)/0.64 BaTi_4 0_9+0.36 BaPr_2 Ti_4 O_(12) composites

The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that the system is composed of BaTi_4O_9 and BaPr_2Ti_4O_(12) two phases. Pr ions are distributed in the BaWi_4O_9 grains and the segregation of Pr ions was observed on the grain boundaries of BaTi_4O_9/BaTi_4O_9. The content of Ti~(3+) and Ti~(2+) decrease in the BPT system composites due to the addition of BaTi_4O_9 fibers, which improved the dielectric properties of the system. BPT10 sample with 10% BaTi_4O_9 fibers, has the best dielectric properties in the system, its ε_r = 64, tan δ= 1×10~(-4)(at 1 MHz) , and it may be a potential candidate for microwave dielectric ceramics.     

Microwave sintering of Ca0.6La0.2667TiO3 microwave dielectric ceramics

Ca0.6La0.2667TiO3 ceramics were prepared by conventional and microwave sintering techniques and their sinterability,microstruc-ture,and microwave dielectric properties were investigated in detail for comparison.Densified Ca0.6La0.2667TiO3 ceramics were obtained by microwave sintering at 1350oC for 30 min and by conventional sintering at 1450oC for 4 h.An unusual phenomenon was found that some larger grains(grain size range:8-10 μm) inclined to assemble in one area but some smaller ones(grain size range:2-4 μm) inclined to gather in another area in the microwave sintered ceramics.The microwave dielectric properties of Ca0.6La0.2667TiO3 ceramics prepared by micro-wave sintering at 1350oC were as follows:dielectric constant(εr) = 119.6,quality factor(Qf) = 17858.5 GHz,and temperature coefficient of resonant frequency(τf) = 155.5 ppm/oC.In contrast,the microwave dielectric properties of the ceramics prepared by conventional sintering at 1450oC were εr = 117.4,Qf = 13375 GHz,and τf = 217.2 ppm/oC.     

CoFe_2O_4/Ba_(0.8)Sr_(0.2)TiO_3异质结磁电复合薄膜的制备与多铁性能

利用射频磁控溅射法在Pt(200)/TiO_2/SiO_2/Si衬底上沉积CoFe_2O_4/Ba_(0.8)Sr_(0.2)TiO_3异质结层状磁电复合薄膜(Ba_(0.8)Sr_(0.2)TiO_3作为底层,CoFe_2O_4作为顶层)。X射线衍射表明CoFe_2O_4/Ba_(0.8)Sr_(0.2)TiO_3异质结复合薄膜是多晶的,由钙钛矿Ba_(0.8)Sr_(0.2)TiO_3相和尖晶石Co Fe2O4相组成。场发射扫描电镜表明在CoFe_2O_4薄膜和Ba_(0.8)Sr_(0.2)TiO_3薄膜之间有明显的界面。复合薄膜的介电常数随频率的变化关系显示了介电色散。复合薄膜表现为良好的铁电性和铁磁性共存。另外,复合薄膜具有直接的磁电耦合效应,磁电电压系数αE先随着偏置磁场Hdc的增大而增大,当偏置磁场Hdc增加到5.6 k Oe,复合薄膜达到最大的磁电电压系数,其值αE=8.7 m V/(cm·Oe),然后随着偏置磁场Hdc的进一步增大,磁电电压系数αE反而减小。     

Effect of Sintering Temperature on Low Frequency Response Properties of Ba_(0.6)Sr_(0.4)TiO_3 Ceramic

Ba_(0.6)Sr_(0.4)TiO_3 ceramic was synthesized by the sol-gel method combined with the solidstate reaction. Phase composition and microstructure analyses indicate that pure BST phase with aggregated nanograins can be achieved. The dielectric properties change with sintering temperature, and reach the maximum at suitable temperatures. The highest dielectric constant of 4351 is obtained at 100 Hz for 1 275 ℃ sintered sample that is 2 times greater than that of the original sample, which indicates the dielectric properties can be modulated by grain size and density. The results show that Ba_(0.6)Sr_(0.4)TiO_3 is a promising candidate for microwave applications.     

Synthesis and Dielectric Properties of Ba_3NaBiNb_(10)O_(30) Ceramics

1　ＩｎｔｒｏｄｕｃｔｉｏｎＦｅｒｒｏｅｌｅｃｔｒｉｃｓｗｉｔｈｔｈｅｔｕｎｇｓｔｅｎｂｒｏｎｚｅｔｙｐｅｓｔｒｕｃｔｕｒｅｈａｖｅｅｘｃｅｌｌｅｎｔｆｅｒｒｏｅｌｅｃｔｒｉｃ ,ｐｉｅｚｏｅｌｅｃｔｒｉｃ ,ｐｙｒｏｅｌｅｃｔｒｉｃ ,ｅｌｅｃｔｒｏ ｏｐｔｉｃ ,ａｎｄｎｏｎｌｉｎｅａｒｏｐｔｉｃａｌｐｒｏｐｅｒｔｉｅｓ[1,2 ] .Ｔｕｎｇ ｓｔｅｎｂｒｏｎｚｅｓｔｒｕｃｔｕｒｅｃｏｎｓｉｓｔｓｏｆａｎａｓｓｅｍｂｌａｇｅｏｆｃｏｒｎｅｒ ｓｈａｒｅｄ [ＭＯ6 ]ｏｃｔａｈｅｄｒａｌ (Ｍ =Ｔｉ,Ｎｂ ,Ｔａ ,ｏｒ…     

Crystallization and Electrical Properties of (Ba_(0.4)Pb_(0.3))Sr_(0.3)TiO_3 Thin Film by Pulsed Laser Deposition

(Ba_(0.4)Pb_(0.3))Sr_(0.3)TiO_3 thin films were fabricated via pulsed laser deposition(PLD)technique on Pt/TiO_2/SiO_2/Si substrate.The crystallization of the films was characterized by XRD and FSEM,and the experimental results suggested deposition parameters,especially the deposition temperature was the key factor in forming the perovskite structure.The dielectric properties of the film deposited with optimized parameters were studied by an Agilent 4294A impedance analyzer at 1 MHz.The dielectric constant was 772,and the loss tangent was 0.006.In addition,the well-shaped hysteresis loop also showed that the film had a well performance in ferroelectric.The saturated polarization P,remnant polarization Pr and coercive field E were about 4.6μC/cm~2,2.5μC/cm~2 and 23 kV/cm(the coercive voltage is 0.7 V),respectively.It is suggested the film should be a promising candidate for microwave applications and nonvolatile ferroelectric random access memories (NvFeRAMs).     

Low-temperature sintering and microwave dielectric properties of Li2MgTi3O8 ceramics doped with BaCu（B2O5）

The influences of BaCu(B₂O₅) (BCB) addition on sintering, microstructure and microwave dielectric properties of Li₂MgTi₃O₈ ceramics were investigated using X-ray diffractometry, scanning electron microscopy and microwave dielectric measurements. The experimental results show that a small amount of BaCu(B₂O₅) addition can effectively reduce the sintering temperature to 900 °C, and induce only a limited degradation of the microwave dielectric properties. Typically, the best microwave dielectric properties of ɛ _r=24.5, Q×f =24 622 GHz, τ _f=4.2×10⁻⁶ °C⁻¹ are obtained for 1.0% BCB-doped Li₂MgTi₃O₈ ceramics sintered at 900 °C for 3 h. The BCB-doped Li₂MgTi₃O₈ ceramics can be compatible with Ag electrode, which may be a strong candidate for low temperature co-fired ceramics applications.     

中温烧结Mg_4Nb_2O_9-CaTiO_3陶瓷相结构的研究

采用传统固态反应方法制备了(1-x)Mg4Nb2O9+xCaTiO3[(1-x)MN-xCT]复合陶瓷。探讨了烧结温度、组分x对Mg4Nb2O9/CaTiO3复合材料相结构的影响。通过XRD和EDS进行物相分析。实验结果表明:V2O5添加能够有效降低Mg4Nb2O9/CaTiO3陶瓷的烧结温度;(1-x)MN-xCT复相的形成主要取决于烧结温度和x的含量。1150℃烧结、0.5≤x≤0.7范围内,形成了Mg4Nb2O9/CaTiO3复相,无新相生成,但元素在不同相之间发生了扩散。     

CuO-TiO2复合纳米粉制备及其原位掺杂Al2O3微波介质陶瓷

研究了CuO-TiO₂复合纳米粉制备方法以及原位掺杂Al₂O₃微波介质陶瓷.采用溶胶-凝胶法低温合成出平均粒径为50 nm的CuO-TiO₂复合纳米粉体.CuO-TiO₂凝胶在Al₂O₃粉体表面形成均质的胶状体,胶状体在750 ℃热处理后,原位形成CuO-TiO₂纳米粒子,温度升高到1 030 ℃左右,生成CuO-TiO₂低熔点化合物,促使Al₂O₃烧结温度降至1 320 ℃,剩余的TiO₂ 均匀分布在Al₂O₃ 陶瓷中,起调节频率温度系数作用.掺杂摩尔分数为0.5%的CuO和10%的TiO₂的Al₂O₃ 陶瓷在1 320 ℃烧结3 h,具有良好的介电性能：介电常数为10.92, 品质因子为30 540 GHz, 频率温度系数为-5.6×10-6/℃.     

Dielectric and Piezoelectric Properties of 0-3 PZT/PVDF Composite Doped with Polyaniline

Lead zirconate titanate （ PZT ） / polyvinylidene fluoride （PVDF） 0-3 piezoelectric composites doped with polyaniline （PANI） were obtained by hot-press method. The polarization properties of the composites were characterized by XRD and P- E hysteresis loops at room temperature. And the dielectric and piezoelectric properties were also measured. The results show that the poling of PZT could be effectively carried oat and the dielectric constant e, and dissipation tanδ increase monatonously by increasing the volume fraction of PANI in the composite. The piezoelectric constant d33, and the planar electromechanical coupling factor kp increase while the mechanical quality factor Qm decreases with the increase in the content of PANI. The d33, kp and Qm show the extremum values at 8 vol%-10 vol% PANI.     

钛酸锶铋介电陶瓷中MgO掺杂研究

本文研究了锶铋钛陶瓷中ＭｓＯ的掺杂效应，发现ＭｇＯ对材料的相结构和介电性能产生很大影响，随ＭｇＯ含量的增加，材料介电温度稳定性提高．作者根据Ｋ．Ｌｉｃｈｔｅｎｅｃｈｅｒ规则以及元素替代效应，讨论了ＭｇＯ相、材料体内元素替代以及电荷施受主补偿对材料缺陷机构和介电性能的影响．     

Improved Breakdown Strength in(Ba_(0.6)Sr_(0.4))_(0.85)Bi_(0.1)TiO_3 Ceramics with Addition of CaZrO_3 for Energy Storage Application

(Ba_(0.6) Sr_(0.4))_(0.85) Bi_(0.1) TiO_3 ceramics doped with x wt%CaZrO_3(x= 0-10) were synthesized by solid-state reaction method. The effects of CaZrO_3 amount on the dielectric properties and structure of(Ba_(0.6)Sr_(0.4))_(0.85) Bi_(0.1) TiO_3 ceramics were investigated. X-ray diffraction results indicated a pure cubic perovskite structure for all samples and that the lattice parameter increased till x=5 and then slightly decreased. A homogenous microstructure was observed with the addition of CaZrO_3. Dielectric measurements revealed a relaxor-like characteristic for all samples and that the diffusivity γ reached the maximum value of 1.78 at x=5. With the addition of CaZrO_3, the dielectric constant dependence on electric field was weakened, insulation resistivity enhanced and dielectric breakdown strength improved obviously and reached 19.9 k V/mm at x=7.5. In virtue of low dielectric loss(tan d0.001 5), moderate dielectric constant(er 1 500) and high breakdown strength(E_b 17.5 k V/mm), the CaZrO_3 doped(Ba_(0.6)Sr_(0.4))0.85 Bi_(0.1) TiO_3 ceramic is a potential candidate material for high power electric applications.     

La2O3、Cr2O3共掺杂的CCTO陶瓷介电性能研究

采用氧化物混合工艺制备了La2O3和Cr2O3共掺杂的CaCu3Ti4O12(CCTO)陶瓷材料。通过XRD、介电温度特性等测试手段,研究了掺杂不同浓度的La2O3和Cr2O3对CCTO体系陶瓷介电性能的影响,并对掺杂机理进行了分析.研究结果表明:分别掺杂La2O3和Cr2O3的CCTO陶瓷的介电损耗为～0.2,比纯的CCTO陶瓷样品低,而介电常数仍保持在～104;掺杂0.03at%La2O3和0.08at%Cr2O3的CCTO陶瓷材料的介电常数为4.4×104,介电损耗可降至0.15.因此,通过共掺杂的方法可以在有效降低CCTO陶瓷介质损耗的同时,仍维持高的介电常数.     

Preparation, Characterization and Dielectric Properties of Ba_6Mg_(0.67)Nb_(9.33)O_(30) Ceramic

1IntroductionSince the discovery of ferroelectricity andrelated prop-ertiesin BaTiO3,alarge amount of research workonoxides,insearch of novel materials for industrial applications,hasbeen done.High performance dielectric ceramics is appliedas key material…     

(Ba_(0.75)Sr_(0.25)(Ti_(1-y)Mn_y)O_3陶瓷的结构相变

Mn掺杂及其价态变化可引起钛酸锶钡陶瓷有趣的结构相变,对低损耗陶瓷材料的开发具有重要的研究价值.采用冷压陶瓷技术在1 380℃/5 h烧结条件下制备了Mn掺杂(Ba0.75Sr0.25)TiO3陶瓷.利用X射线衍射(XRD)确定晶体结构,研究Mn掺杂对(Ba0.75Sr0.25)TiO3陶瓷结构的影响.研究表明,随Mn掺杂量的增加,(Ba0.75Sr0.25)(Ti1-y Mn y)O3陶瓷发生四方相→四方-六方混合相→立方-六方混合相的结构相变.     

钛酸锶钡溶胶制备研究

用锶、钡的有机酸盐和钛酸丁酯为原料,以溶胶－凝胶法制备了钛酸锶钡溶胶。考察了有机酸分子量、溶胶的水解方法对交亲润性、湿敏性、二氧化碳敏感性、成膜均匀性、热解性等的影响。实验得出：先将钛酸丁酯的乙酸乙酯溶液部分水解,然后与锶、钡的正辛酸盐、２－乙基已酸盐或壬酸盐的乙酸乙酯溶液充分混合,所得的溶胶具有较好的综合性能。     

纳米TiC对Si3N4基复合陶瓷材料性能和微观结构的影响

用热压法制备了纳米TiC增韧补强的Si₃N₄基复合陶瓷材料,研究了不同TiC含量对复合陶瓷材料力学性能与微观结构的影响.结果表明：纳米TiC颗粒的添加对复合材料的力学性能的提高是有利的,当纳米TiC的质量分数为15%时,复合材料具备较优的力学性能,其抗弯强度、断裂韧性、HV硬度分别达到895MPa,8.03MPa.m1/2,15.06GPa;不同尺寸的Si₃N₄晶粒形成双峰结构,有利于复合材料性能的提高;其断裂机制为沿晶断裂和穿晶断裂的混合类型.     

Mg掺杂对 Ba0.6Sr0.4TiO3薄膜介电性能的影响

应用Sol-Gel工艺制备了组份为(1-y)Ba 0.6Sr0.4TiO3-yMgO的薄膜材料,研究了Mg掺杂BST薄膜晶相结构、介电性能以及绝缘性能的影响规律.实验发现随着Mg掺杂量的增加,BST薄膜的介电常数、损耗因子以及电容变化率减小,其电阻率则增加;当Mg掺杂量分数为5%时,其介电常数为380,损耗因子为0.013,电容变化率为17.5%,电阻率为1.0×1012Ω@crm.