BST-SiO2-B2O3系铁电微晶玻璃陶瓷的制备和研究

采用sol-gel工艺制备了(Ba0.5Sr0.5)TiO3(BST)-SiO2-B2O3系铁电玻璃陶瓷。对其显微结构进行了分析,并通过阻抗分析仪测试其介电温谱(–50~+100℃)。结果表明:SiO2-B2O3系BST铁电玻璃陶瓷的相结构为立方钙钛矿相,显微结构呈微晶结构,当BST相与玻璃相的摩尔比为4:1时,颗粒平均粒径为1.35μm。随着SiO2-B2O3玻璃相含量的增加,εr明显降低,同时居里峰宽化,tC向低温方向移动。     

三氧化二钕掺杂量对低温烧结BST陶瓷介电性能的影响

采用固相法,研究了Nd2O3掺杂量对ZBS玻璃添加的Ba0.65Sr0.35TiO3(BST)基低温烧结的陶瓷的物相组成、显微结构及介电性能的影响。结果表明:Nd2O3的掺杂并没有改变低温烧结的BST基陶瓷的物相结构,仍为单一钙钛矿结构。随着Nd2O3掺杂量的增大,BST基陶瓷的介电常数先增大然后减小,介质损耗先减小然后增大。当Nd2O3添加质量分数为1.5%,烧结温度为975℃时,BST基陶瓷的综合性能较好,此时相对介电常数为667,介质损耗为0.01,在–30~+85℃容温变化率为–35.2%~14.8%。     

无碱玻璃改性0.8BaTiO_3-0.2BiYO_3介电陶瓷的研究

采用传统固相法制备Ba-B-Al-Si无碱玻璃改性0.8BaTiO_3-0.2BiYO_3(0.8BT-0.2BiY)的介电陶瓷。研究了无碱玻璃含量对0.8BT-0.2BiY陶瓷微结构和介电性能的影响,无碱玻璃的质量分数分别为x=0,0.01,0.03,0.05,0.07。研究结果表明,玻璃改性后的陶瓷,烧结温度降低,X线衍射(XRD)图谱中均出现第二相,主晶相均仍维持钛酸钡钙钛矿伪立方结构,掺杂玻璃组分的质量分数为3%时,第二相的衍射峰的强度最弱。陶瓷经无碱玻璃改性后,介电常数均减小,居里峰展宽效应减弱,铁电性增强。在玻璃的质量分数低于3%时,极化强度增大,在玻璃的质量分数为3%时最大。     

V_2O_5掺杂MgTiO_3-CaTiO_3陶瓷的介电性能

采用固相反应法制备了V2O5掺杂的MgTiO3-CaTiO3(MCT)介质陶瓷。研究了V2O5掺杂量对陶瓷晶相组成、烧结温度和介电性能的影响。结果表明:V2O5掺杂的MCT陶瓷的主晶相为MgTiO3和CaTiO3两相结构,当掺杂量较低时,有第二相CaVO3产生;V2O5掺杂能降低MCT陶瓷的烧结温度并使其介电性能得到改善。当x(V2O5)为1%时,在1250℃烧结2.5h获得最佳性能:εr为20.17,tanδ为2×10–3,αε为4.9×10–5/℃。     

CaTiO_3掺杂对BST铁电电容器陶瓷性能的影响

采用固相法制备了CaTiO3掺杂的(Ba0.65Sr0.35)TiO3(BST)陶瓷,研究了CaTiO3掺杂量对BST电容器陶瓷介电性能和微观结构的影响。结果表明:随着CaTiO3掺杂量的增加,BST陶瓷的相对介电常数(εr)先增大然后减小然后增大,介质损耗(tanδ)和交流耐压强度(Eb)先增大然后减小。当CaTiO3掺杂量为摩尔分数10%时,BST陶瓷的综合介电性能较好:εr为4480,tanδ为0.022,Eb为5.8×103V/mm(AC),容温特性符合Y5U特性。     

BBS玻璃掺杂对CLST陶瓷介电性能的影响

采用传统陶瓷工艺制备了BaO-B2O3-SiO2(BBS)玻璃掺杂的CaO-Li2O-Sm2O3-TiO2(CLST)介质陶瓷,用X-射线衍射仪,扫描电镜及电感-电容-电阻测试仪等对其烧结特性、相结构及介电性能进行了系统研究.结果表明,BBS掺杂能显著降低CLST陶瓷的烧结温度,由1 300℃降至1 100℃.BBS掺杂量为7%(质量比),烧结温度为1 100℃时,CLST陶瓷具有较好的综合介电性能:介电常数εr=62,介电损耗tan δ=0.007,频率温度系数τf=0.82×10-6/℃.     

Gd_2O_3掺杂对BZT基陶瓷结构和介电性能的影响

以碳酸钡、二氧化钛、二氧化锆等为主原料,以氧化钆为掺杂剂,采用传统固相法分别于1 250,1 280,1 300,1 330℃下制备了BaZr_(0.1)Ti_(0.9)O_3(BZT)+x Gd_2O_3(0≤x≤0.7%)陶瓷样品。XRD结果表明,Gd~(3+)掺杂后的陶瓷样品主晶相不变,均为钙钛矿结构。SEM结果表明,随着Gd3+掺杂量的增加,陶瓷的晶粒尺寸先减小后增大。陶瓷样品的体积密度和介电常数在x=0.2%,0.6%时出现较高值,介质损耗tanδ随Gd~(3+)掺杂量的增大呈减小趋势。Gd_2O_3掺杂改善了BZT陶瓷的介电温度特性,具有一定的移峰与压峰的作用。     

Zn-B玻璃掺杂的(K0.5Na0.44Li0.06)(Nb0.84Ta0.1Sb0.06)O3陶瓷相变及电学性能研究

研究了Zn-B玻璃掺杂的(K0.5Na0.44Li0.06)(Nb0.84Ta0.1Sb0.06)O3(KNLNTS)陶瓷的制备、相变及电学性能.研究发现,Zn-B玻璃能够有效地促进铌酸钾钠基无铅压电陶瓷的烧结特性.XRD结果显示Zn-B玻璃掺杂的KNLNTS陶瓷为正交-四方共存结构,随掺杂量的增加正交结构相的含量逐渐增加;并且降低烧结温度能够有效地抑制第二相的产生.介电温谱测试结果显示Zn-B玻璃掺杂的KNLNTS陶瓷其居里温度先降后增在x=0.1时达到最小值.在1050℃保温5 h条件下烧结可以获得最佳的压电性能:d33=197 pC/N,kp=0.37,εr=975,tanδ=0.028.     

Li_2O-B_2O_3-SiO_2玻璃掺杂对BZN陶瓷介电性能的影响

采用传统的固相反应法制备了Li2O-B2O3-Si O2(LBS)玻璃掺杂的(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7(BZN)陶瓷,研究了LBS作为烧结助剂对BNZ陶瓷的烧结特性、晶相组成、微观结构以及介电性能的影响。结果表明,添加少量LBS玻璃后的陶瓷试样中没有出现第二相,主晶相仍为立方焦绿石结构。烧结助剂能有效降低BZN陶瓷的烧结温度,当LBS质量分数为0.6%时,陶瓷试样的烧结温度降到900℃,制备的试样具有良好的介电性能:相对介电常数为159,介质损耗为8×10–4(1 MHz)。     

富钛型钛酸锶钡基陶瓷的微观结构与介电性能

采用传统固相法制备Nd2O3掺杂富钛型(Ba0.75Sr0.25) Ti1+xO3(x为摩尔比)陶瓷,通过扫描电镜及LCR测试系统,研究不同x值、Nd2O3掺杂量及烧结工艺对钛酸锶钡基陶瓷微观结构与介电性能的影响。结果表明,随着x值及Nd2O3掺杂量增大,陶瓷试样均出现柱状第二相。当x=0.01且w(Nd2O3)=0.4%时,陶瓷试样经1 250 ℃烧结2 h后,其室温相对介电常数(εr)高达8.67×103,介电损耗(tan δ)仅为7.87×10-3。随着x值及Nd2O3掺杂量增大,陶瓷的居里峰显著移动。     

Investigations of Indium Tin Oxide—Barium Strontium Titanate–Indium Tin Oxide Heterostructure for Tunability

This letter reports for the first time the interesting behavior of the interface between indium tin oxide (ITO) as a high resistive electrode and barium strontium titanate tunable paraelectric thin film material. The interface is consisting of barium strontium titanate (BST) thin film dielectric material sandwiched between two ITO high resistive layers, all are integrated above glass substrate. When dc field is applied between the ITO layers, the BST thin film material properties are tuned. It is found that the ITO/BST/ITO heterostructure exhibits a tunable resistor performance. To our knowledge; these results are never reported.     

Low-Temperature Sintering of Ba0.5Sr0.5TiO3-SrMoO4 Dielectric Tunable Composite Ceramics for LTCC Applications

A sintering-aid system using melting of B-Li glass for barium strontium titanate (BST)-based compositions to be used in low-temperature cofired ceramic (LTCC) layers is introduced. The effects of the sintering aid on the microstructure, dielectric properties, and application in LTCC were investigated. The composition Ba_0.5Sr_0.5TiO₃-SrMoO₄ with 3 wt.% B-Li glass sintered at 950°C exhibits optimized dielectric properties, including low dielectric constant (368), low dielectric loss (0.007), and moderate tunability (13%, 60 kV/cm) at 10 kHz. At 1.44 GHz, it possesses a dielectric constant of 218 and Q value of 230. LTCC multilayer ceramic capacitors fabricated by the tape-casting process have steady relative tunability of 12% at 300 V, suggesting that BST50-SrMoO₄-B-Li glass composite ceramic is a promising candidate for electrically tunable LTCC microwave device applications.     

Co掺杂对BST薄膜介电性能的影响

用sol-gel法在Pt/Ti/SiO2/Si(100)衬底上制备了掺Co的钛酸锶钡(BST)薄膜,研究了Co的掺杂量x(Co)对BST薄膜的晶相结构和电学性能的影响。结果表明:随着x(Co)的增加,BST薄膜的介电常数εr,介质损耗tgδ和漏电流密度JL均降低;当x(Co)为5%时,BST薄膜的εr、tgδ、JL、可调性和品质因子分别为:228.3、0.013、3.69×10–7 A/cm2、15.4%、12.03。     

ZnO-B_2O_3玻璃对Mg_2TiO_4微波介质陶瓷结构和性能的影响

利用传统固相烧结法制备了ZnO-B2O3玻璃掺杂的Mg2TiO4微波介质陶瓷,研究了ZnO-B2O3玻璃掺杂对所制陶瓷相成分、微观形貌和微波介电性能的影响。结果表明:ZnO-B2O3玻璃掺杂能使Mg2TiO4陶瓷的致密化温度降低200℃左右。当Mg2TiO4中掺杂质量分数2%的ZnO-B2O3玻璃时,经1 300℃烧结所得陶瓷微波性能较好:εr=13.62、Q.f=101 275 GHz、τf=–51×10–6/℃。     

MgO掺杂对Ba0.6Sr0.4TiO3陶瓷性能的影响

采用常规陶瓷加工成型及烧结工艺,研究了在Ba0.6Sr0.4TiO3(BST)陶瓷中掺杂1.0%,20.0%,40.0%,60.0%(质量分数)的MgO后介电性能的变化规律。又通过对微波介质性能的测量,绘制出Ba0.6Sr0.4TiO3(BST)陶瓷随温度变化的相变图及其介电常数和可调谐率随MgO掺杂量变化的曲线。     

Preparation and characterization of Si-doped barium titanate nanopowders and ceramics

Si-doped barium titanate nanopowders and ceramics were prepared through the sol-gel process. The powders and ceramics were characterized by methods of XRD, SEM and TEM. The dielectric properties of the ceramics were also determined. The results indicated that the powders were nanopowders and they were all cubic BaTiO₃ phase with the concentration of Si ?5.0 mol%. When the concentration of Si increased to 10.0 mol%, another phase of Ba₂TiSi₂O₈ appeared. After sintering, the cubic BaTiO₃ phase was transformed into tetrahedron BaTiO₃ phase. Si doping with low concentration resulted in improving grain growth and reduced dielectric loss. As the sintering temperature increased, the dielectric properties of the ceramics decreased. BaTiO₃ ceramics doped with Si all had a small peak at room temperature in ε−T cures. Specially, the ceramic doped with 0.3 mol% Si had evident double peaks, the maximum room temperature permittivity (4081) and the minimum dielectric loss (0.004).     

BST薄膜非线性特性及机理研究

钛酸锶钡(BaxSr1-xTiO3,简称BST)薄膜具有非线性强、漏电流小、居里温度可调等特点,因而在介质移相器、压控滤波器等方面有着广泛的应用前景。笔者对BaxSr1-xTiO3(x=0.45~0.90)系列陶瓷的晶体结构和介电性能、膜厚均匀性控制、BST薄膜的微结构(包括组成、晶体结构和电畴等)和介电非线性尺度效应、铁电薄膜介电非线性模型、薄膜型介质移相器的设计和制作等重要问题进行了研究,取得了以下研究结果:通过研究靶基中心不重合的磁控溅射系统,建立了平面磁控溅射膜厚分布的数学模型,提出了采用T=∫Ld(x,y)ds=∫0td(ξ(t),ψ(t))ξ'2(t)+ψ'2(t)dt来描述靶基中心不重合的平面磁控溅射的膜厚分布情况。在靶基距为72mm、公自转转速比为5.3的条件下,采用自行设计的射频磁控溅射设备和φ100mm靶材制备的BST薄膜膜厚均匀性偏差为2.8%。采用压电力显微镜(PFM)研究了BST薄膜中电畴的类型和尺寸。不仅证实BST薄膜中存在90°铁电畴,而且确定了BST薄膜由多畴转变为单畴结构的晶粒临界尺寸(单畴临界尺寸)为31nm左右。通过研究BST薄膜的介电非线性尺度效应,发现晶粒尺寸和膜厚对薄膜的介电非线性具有重要的作用。随着晶粒尺寸和膜厚的增加,BST薄膜的介电系数、介电系数变化率都逐渐增大。晶粒尺寸对单畴态薄膜的介电系数电压变化率和矫顽场强影响特别显著,而对多畴态薄膜的介电系数电压变化率和矫顽场强影响不明显。在上述实验研究的基础上,对铁电材料的介电非线性机理进行了研究。首先,从简单、实用的角度出发写出表征P(E)和ε(E)非线性的数学多项式,根据介电偏压特性曲线和电滞回线的特征值和连续性原理,给出边界条件和初始条件,解出表达式中的各项系数,从而建立了铁电晶体的介电非线性模型。然后,采用理想的晶粒–晶界几何模型,画出铁电陶瓷材料的等效电路,引入晶粒和晶界的大小,从而建立了铁电陶瓷的介电非线性模型。再采用理想二极管等效界面势垒,得到薄膜型平板电容器等效电路,引入膜厚和界面厚度两个尺度变量,从而建立了铁电薄膜的介电非线性模型。最后,利用文献的数据和曲线对模型进行了验证,模拟得到的曲线与实验得到的曲线变化趋势基本一致,表明该模型可以较好地解释铁电材料(包括陶瓷和薄膜)的介电非线性特性及其随晶粒大小、膜厚和界面厚度等尺度变化的规律。对薄膜型介质移相器的设计、制作和测试进行了研究。采用ADS和HFSS软件进行仿真,设计出了分布式电容负载型铁电薄膜介质移相器的电路结构和各部分的尺寸;采用改进的剥离工艺,制作出了电极线条整齐的铁电薄膜介质移相器;采用矢量网络分析仪,在频率为35GHz、控制电压为40V条件下,测得介质移相器的移相度为180°,插损为9.7dB。     

新型低插损的铁电移相材料

实验研究了Bi2O3掺杂量对钛酸锶钡/氧化镁复合体系介电常数、介质损耗等性能的影响。结果表明控制掺杂Bi2O3质量分数在0.25%左右时,Ku频段f在12~18 GHz,εr为170左右,tanδ为0.01左右,材料的电性能得到大大的改善,满足了雷达移相器的应用要求。     

Enhanced Piezoelectric Properties and Tunability of Lead-Free Ceramics Prepared by High-Energy Ball Milling

Zirconium-doped barium titanate Ba(Zr_0.15Ti_0.85)O₃ lead-free ceramics (hereinafter referred to as BZT) were synthesized using the solid-state reaction method by adopting the high-energy ball milling technique. Nanosized BZT powders resulted from high-energy ball milling, which in turn enhanced the dielectric and piezoelectric properties of the ceramics. A single-phase perovskite structure free from secondary phase peaks was observed for sintered BZT samples, and a relative density of ～94% of the theoretical density was achieved. The electric-field-induced polarization-current data indicate the ferroelectric nature of the samples. Unipolar strain as high as 0.12% was realized for the ceramics sintered at 1350°C, indicating their potential for use in actuator applications. Very high tunability of >70% for these ceramics is also reported.     

CBS掺杂对钛酸钡陶瓷介电性能的影响

研究了钙硼硅(CBS)微晶玻璃掺杂BaTiO3(BT)-Nb2O5-ZnO系统的微结构和介电性能,并用掺杂后晶粒壳与晶粒芯体积分数的变化规律分析了其改性机理。对比SEM照片得出,不同含量CBS掺杂BT的室温εr与掺杂后BT陶瓷的晶粒生长情况以及玻璃相的多少和分布密切相关。经优化配方和工艺后,在空气中于1150℃烧成的BaTiO3陶瓷材料的主要性能指标达到:εr25℃>1350,tgδ≤1.0×10-2,ρ≥1011?·cm,最大电容量变化率不超过±10%(-55～+150℃),适于制备中温烧结X8R多层陶瓷电容器。