纳米(Ba,Sr)TiO_3粉体材料的制备

采用溶胶 -凝胶工艺制备了 (Ba ,Sr)TiO3凝胶 ,并利用微波烧结技术对凝胶进行合成和烧结。结果表明 ,获得的 (Ba ,Sr)TiO3粉体颗粒较细 ,与传统固相反应合成法相比 ,其钙钛矿相的合成温度由 110 0℃降至 90 0℃ ;粉体的颗粒尺寸在 5 0nm附近     

The electrostrictive effect and dielectric properties of lead-free 0.5Ba(ZrxTi1−x)O3–0.5(Ba0.75Ca0.25)TiO3 ceramics

Lead-free 0.5Ba(Zr_xTi_1?x)O₃–0.5(Ba_0.75Ca_0.25)TiO₃ (x = 0.25, 0.30, 0.35, 0.40) ceramics have been synthesized by a conventional solid state sintering method. The room temperature ferroelectric and electrostrictive properties of these ceramics were studied. Based on the measured properties, these ceramics showed a typical relaxor behavior. The Curie temperature of BZT–BCT ceramics decreases with increasing the Zr content. The largest electrostrictive strain and electrostrictive coefficient are founded in BZT–BCT ceramic with x = 0.25, the value is 0.16 % and 0.079 m⁴ C^?2, respectively. The polarization, electrostrictive strain and electrostrictive coefficient (Q ₁₁) decrease with increase in Zr concentration. For samples with low Curie temperature, which have large room temperature dielectric constant (ε), electrostrictive coefficient increases (Q ₁₁) is smaller. Because doping can disrupt the long range cation order, and electrostrictive (Q ₁₁) coefficient increases with cation order from disordered, through partially-ordered, simple relaxor and then ordered perovskites, ferroelectrics with a disordered structure have a huge permittivity, but a small electrostrictive coefficient (Q ₁₁).     

Ba(Ti0.96Sn0.04)O3陶瓷的物性研究

采用传统固相反应法制备了Ba(Ti_0.96Sn_0.04)O₃无铅压电陶瓷, 对其压电性能、介电性能、铁电性能和微观结构等进行了研究。研究发现, 原料以及制备工艺对Ba(Ti_0.96Sn_0.04)O₃陶瓷的压电性质具有较大的影响。与BaTiO₃陶瓷相比, Ba(Ti_0.96Sn_0.04)O₃陶瓷的正交-四方相变温度T_O-T得到了一定的提高, 并且T_O-T附近的热滞只有1.8℃。陶瓷的微观形貌呈现出较为复杂的畴结构, 主要以90°平行带状畴为主, 偶尔有少量不同构型的180°畴。电滞回线呈现为理想的近似矩形饱和形状的曲线, 剩余极化强度P_r为18.9 μC/cm², 矫顽场E_c为 2.5 kV/cm。此外, 非180°畴的翻转是引起陶瓷逆压电常数d₃₃^*的主要因素, 其值可达550 pm/V。     

Ba3Gd(PO4)3:Eu3+荧光粉的合成及发光性质

采用高温固相反应法合成了不同Eu³⁺掺杂浓度的Ba₃Gd(PO₄)₃荧光粉。利用X射线衍射对产生的晶体结构进行了分析, 证实产物为纯相, Eu³⁺的引入没有导致晶体结构的改变。利用Van Uitert模型对⁵D₀能级荧光的浓度猝灭行为进行了研究, 发现浓度猝灭是由于Eu³⁺间交换相互作用所导致。分析了⁵D₀荧光发射的温度依赖, 给出了荧光温度猝灭行为符合横向穿越模型, 并通过非线性拟合获得了激活能。利用Eu³⁺的发射光谱和荧光衰减数据, 计算了⁵D₀→⁷F_J辐射跃迁速率及荧光分支比, 同时得到了光学跃迁强度参数。     

不同掺杂对Ba3Y(BO3)3晶体的生长和相变的影响

结合X射线粉末衍射和差示扫描量热法,系统研究了不同格位上的掺杂对Ba₃Y(BO₃)₃晶体的生长和相变的影响. 研究发现,相同掺杂浓度10at%时,掺Nd³⁺的α-Ba₃Y(BO₃)₃晶体的相变温度（1099.6℃）比掺Yb³⁺的晶体的相变温度（1145.3℃）低;且随着掺Nd³⁺浓度的降低,晶体的相变温度升高,晶体在降温过程中更容易发生相变. 在晶体中掺入Sr²⁺离子,可以有效提高Yb³⁺∶α-Ba₃Y(BO₃)₃晶体的稳定性. 随着Sr²⁺掺入浓度的增加,晶体的熔点升高,相变温度降低. 当Sr²⁺掺杂浓度为16at%时,晶体的相变峰消失;当Sr²⁺掺杂浓度分别为5at%、10at%时,晶体仍然发生相变.     

La2/3(Ca,Ba)1/3MnO3系统的顺磁共振研究

报道了对La_2/3Ca_1/3MnO₃和La_2/3Ba_1/3MnO₃系统不同温度下的电子顺磁共振(EPR)实验研究,当温度高于某一特征温度Tmin时,共振线宽随温度降低而线性变窄;当温度低于Tmin时,共振线宽表现出反常展宽.基于“瓶颈(bottleneck)”自旋-晶格弛豫模型我们对这种行为进行了讨论,并且指出A位离子平均半径强烈影响着自旋-晶格交换作用和自旋-自旋相互作用的强弱.     

PHASES AND PROPERTIES OF SYSTEM Pb(Zn_(1/3)Nb_(2/3))O_3—PbTiO_3 —Ba(Ti(0.85)Sn(0.15))O_3

本文合成并研究了Pb(Zn_(1/3)Nb_(2/3))O_3-PbTiO_3-Ba(Ti_(0.85)Sn_(0.15))O_3(PZN-PT-BTS)陶瓷的晶相组成及其介电、压电和铁电性能。Sn~(4+)离子的存在,使PZN-PT-BTS 陶瓷晶粒难以具有完全的钙钛矿结构。微量焦绿石的存在,对其电性能的影响并不很大。PZN-PT-BTS 具有良好的介电、压电和铁电特性。     

Dielectric properties of sol–gel synthesized SrTiO3/(Ba0.7Sr0.3)TiO3 and SrTiO3/Ba(Zr0.3Ti0.7)O3 thin film heterostructures

The paper presents synthesis of Ba_0.7Sr_0.3TiO₃ (BST), BaZr_0.3Ti_0.7O₃ (BZT) and SrTiO₃ (ST) thin films and their heterostructures using modified Pechini method. The La_0.7Sr_0.3MnO₃ has been used as a conducting bottom layer to form metal ferroelectric metal capacitor. The thin films are spin coated on SiO₂/n-Si(100) substrates. The thin films thus deposited are characterized for crystal structure, morphology, dielectric, complex impedance and admittance properties. Deposition of surface layer ST is observed to reduce loss tangent tan δ of BST and BZT thin films, still maintaining equivalent magnitude of figure of merit γ. The results on dielectric properties are analyzed in terms of the Maxwell–Wagner model and Koop’s phenomenological theory.     

无铅Ba(Ce,Ti)O_3陶瓷的电卡效应

本文使用标准固相烧结法制备了Ba(Ti_(1-x)Ce_x)O_3(x=0.10,0.15,0.20)陶瓷,通过XRD分析发现这些陶瓷中除了Ba(Ti_(1-x)Ce_x)O_3主相外,还存在少量的杂相。利用Rietveld拟合的方法,获得了Ba(Ti_(1-x)Ce_x)O_3主相中的Ce/Ti实际比例。介电温谱表明这些陶瓷均存在一个明显的介电峰,且随着x的增加,峰值温度下降,介电峰宽展宽。利用不同温度下的电滞迴线,给出了不同温度和电场强度下的极化值,通过间接法获得了这些陶瓷的电卡效应。结果表明,BaTi_(0.9)Ce_(0.1)O_3的电卡效应最强,其DT值在403K和40kV/cm的电场下达到最大值,为0.48K,电卡强度为0.12×10~(-6)K·m/V。     

液相包覆法合成Ba(Mg1/3Ta2/3)O3超细粉体

以水合五氧化二钽(Ta2O5·nH2O)纳米胶粒为活性固相基体,柠檬酸镁、柠檬酸钡混合溶液为包覆相,采用液相包覆-界面反应的方法制备Ba(Mg1/3Ta2/3)O3超细粉体.利用热失重-差热分析、X射线衍射及透射电镜等手段对产物的合成过程与结构形态进行了分析表征.研究表明以该方法能够在800℃下合成出成分均一、纯度较高、具有良好烧结活性的BMT超细粉体,产物粒子的形态接近球形,粒径分布窄,大约为20～30nm.     

用柠檬酸盐-凝胶法低温合成单相Ba(Mg_(1/3)Ta_(2/3))O_3

本文利用XTD、DTA、TGA、SEM、TEAI等分析手段研究了用柠檬酸盐-凝胶法低温（600℃）合成单相Ba（Mg1／3Ta2／3）O3的方法,结果发现，与传统的固相反应合成BMT的方法相比，柠檬酸盐溶胶-凝胶法能在600℃的温度下合成单相BAT，合成的粉体具有10～20nm的单颗粒尺寸．     

CaRuO3电极对(Ba,Sr)TiO3薄膜的介电特性的影响

在Pt(111)/Ti/SiO2/Si(100)衬底上,用脉冲激光沉积工艺分别制备出了(110)外延取向生长的(Ba0.65Sr0.35)TiO3/CaRuO3(BST/CRO)异质结构薄膜;BST/CRO异质结构薄膜由纳米晶团簇组成,最大的团簇晶粒达500 nm,平均晶粒尺寸在60～80 nm,薄膜厚度为650 nm.BST/CRO异质结薄膜均为表面平滑和致密结构.BST/CRO异质结薄膜的介电常数和介电调谐率分别高达851和78.1%.与纯BST薄膜比较,用CRO作电极,增益介电常数与介电调谐率.     

Yb_2O_3的掺杂方式对Ba(Ti_(1-y)Zr_y)O_3陶瓷介电性能的影响

在Ｂａ（Ｔｉ１－ｙＺｒｙ）Ｏ３中,Ｙｂ２Ｏ３的不同掺杂方式引起了材料性能的显著变化．采用 Ｂａ（Ｔｉ１－ｙＺｒｙ）Ｏ３合成后Ｙｂ２Ｏ３的适量掺杂,陶瓷介温峰明显地移动,介电常数大幅度提高, 获得了室温介电常数＞２５０００,１２５０℃左右烧成,符合Ｙ５Ｖ标准的高介材料．合成后掺杂的 Ｙｂ２Ｏ３,使材料介电常数提高,可能与施主掺杂引入的局域化电子有关．合成前掺杂Ｙｂ２Ｏ３ 的样品,介电常数较低,移峰效率偏小,可能是Ｙｂ的Ｔｉ位受主取代使施主引入的局域化电子 得到补偿的结果．     

Microwave characterization of nanostructured ferroelectric Ba(0.6)Sr(0.4)TiO(3) thin films fabricated by pulsed laser deposition

A series of nanostructured ferroelectric thin films of barium strontium titanate were fabricated using a pulsed laser deposition system with real-time in?situ process control. Pulsed laser deposition parameters were controlled during the growth of nanostructured thin films for use in the development of high frequency tunable microwave devices. The thin films were all grown at the same substrate temperature and laser beam energy density, but the chamber oxygen partial pressure (COPP) was varied systematically from 19?mTorr through 1000?Torr. Structural and electromagnetic characterization was performed using atomic force microscopy and evanescent microwave microscopy, respectively. Atomic force microscopy showed a linear increase in grain size with increases in the ambient oxygen pressure from 38 to 150?mTorr and from 300?mTorr to 1000?Torr. The correlation of the microwave properties with the epitaxial film microstructure can be attributed to stresses and polarizability in the film. Microwave characterization showed that a COPP of 75?mTorr yielded the most desirable film in terms of tunability and loss tangent over a wide frequency range.     

Microwave dielectric properties of Ba(Sn x Zn(1−x)/3Nb(1−x)2/3)O3 (0 ⩽ x ⩽ 0.32) ceramics

The dielectric properties of the (1–x)Ba(Zn_1/3Nb_2/3)O₃–xBaSnO₃ (0 x 0.32) composition at microwave frequencies were investigated in this study. With the addition of BaSnO₃, the dielectric Q(Q _d) value of Ba(Zn_1/3Nb_2/3)O₃ (BZN) can be improved and a small temperature coefficient of resonant frequency (_f) can be achieved. When 22.6 mol % of Sn is added to BZN, the characteristics of the Ba(Sn_0.226Zn_0.258Nb_0.516)O₃ ceramics sintered at 1500°C are as follows: dielectric constant _r = 32, _f = + 12 p.p.m.°C¹ and high Q _d value of 9700 at 10 GHz. Based on the classical dispersion theory and the logarithmic mixing rule, the effects with additions of substitutional element of BaSnO₃ on the microwave dielectric properties of Ba(Zn_1/3Nb_2/3)O₃ can be mostly explained.     

影响Ba(B'1/3 B'2/3)O3型微波介质陶瓷介电损耗的因素

微波介质陶瓷是制作各种微波器件的关键材料.具有复合钙钛矿结构Ba(B'1/3B"2/3)O3(B'=Mg、Zn、Ni或Co;B"=Ta和Nb)型的微波介质陶瓷材料由于在很高的微波频率下具有极低的介电损耗而受到人们的重视.在总结前人研究成果并结合自己研究结果的基础上,从材料的晶体结构、显微组织、制备工艺等方面探讨了影响这类材料介电损耗的因素.     

Piezoelectric and pyroelectric properties of (Bi0.5Na0.5)0.94Ba0.06TiO3/P(VDF-TrFE) 0–3 composites

Bismuth sodium barium titanate [(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ or BNBT] ceramic powder have been incorporated into a polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE) 70/30 mol%] copolymer matrix to form 0–3 composites. With the composition near the MPB region, BNBT has relatively high piezoelectric and dielectric properties. P(VDF-TrFE) ferroelectric copolymer films can be poled to give piezoelectric and pyroelectric performance without prior mechanical stretching. The composites were prepared using solvent casting to disperse the ceramic powder homogeneously in the copolymer matrix. Composites with BNBT volume fraction ϕ ranging from 0.05 to 0.30 were fabricated using a hot-press method. The piezoelectric and pyroelectric coefficients of the composites were studied as a function of ϕ under different poling conditions. As BNBT has a low relative permittivity, so it is relatively easy to pole the BNBT ceramic inclusion. Hence, the BNBT 0–3 composites were found to have better pyroelectric properties than that of the lead zirconate titante PZT/P(VDF-TrFE) 0–3 composites.     

(Bi0.5Na0.5)0.935Ba0.065TiO3-xBiScO3陶瓷储能及应变性能研究

本研究采用BiScO₃组分对固相烧结工艺制备的(1-x)(Bi_0.5Na_0.5)_0.935Ba_0.065TiO₃-xBiScO₃(BNBT-xBS)无铅陶瓷进行改性, 考察了BiScO₃掺杂含量对陶瓷的微观结构、储能、场致应变和介电等性能的影响。结果表明: 随着BiScO₃掺杂含量的增加, BNBT-xBS陶瓷的相结构由三方相与四方相共存演变为伪立方相, 无杂相形成, 且平均晶粒尺寸略有增大; BiScO₃组分的引入破坏了BNBT陶瓷铁电畴的长程有序, 表现出弱极化, 且伴随有铁电相到弛豫铁电相的相变过程。BiScO₃组分提高了储能和应变性能, 在70 kV/cm电场下其最大储能密度为0.46 J/cm³, 电致应变达到0.25%。介电常数随着掺杂含量的增加逐渐降低, 其介电行为也表明陶瓷具有弛豫铁电体特征; BNBT-xBS陶瓷表现出负温度系数效应, 且在450℃以下具有较好的绝缘性。     

CaTiO3对(Ba,Pb)TiO3系高温PTC材料性能和显微结构的影响

本文研究了CaTiO3含量及烧成工艺对(Ba,Pb) TiO3基PTC陶瓷材料性能和显微结构的影响.结果表明CaTiO3的最佳添加量为3mol％,室温电阻率达到最小,PTC效应最好.SEM观察表明添加CaTiO3后晶粒更均匀致密.不同烧成工艺下材料性能的比较,结果表明烧成温度越高,温度系数越大,但室温电阻率也越大；降温...     

添加剂MnCO_3和BazrO_3对Ba(Zn_(1/3) Nb_(2/3))O_3陶瓷烧结温度和介电性能的影响

采用传统的固相烧结法制备Ba(Zn_(1/3) Nb_(2/3))O_3(BZN)和(1-x)Ba(Zn_(1/3)Nb_(2/3))O_3-xSr(Zn_(1/3)Nb_(2/3))O_3(BSZN)陶瓷,研究MnCO_3和BaZrO_3添加剂对其烧结温度和介电性能的影响。研究表明二者均是很好的助熔剂,在烧结过程中形成液相促进原子扩散从而降低烧结温度,本研究中的最佳烧结温度为1260℃(5#样品)。MnCO_3和BaZrO_3对于改善系统的介电性能均有较好的效果,合理调整添加剂的用量可以有效的改善介电性能。0.35BZN-0.65SZN-1%MnCO_3样品的介电性能最佳且烧结温度低于1300℃。