Synthesis mechanism of Pr doped BaTi4O9 powder by sol-gel process

Pr Doped BaTi4O9 gel was prepared by sol-gel method using Ti(OC4H9)4, Ba(CH3COO)2, CH3COOH and CH3OCH2CH2OH as raw materials. Through analyzing dry gel thermal treated at different temperatures, the possible synthesis mechanism of Pr doped BaTi4O9 powder was discussed. At first, Ti(OC4H9)4 hydrolyzes and three dimensional networks form, in which Ba2 and CH3COO- are mostly in the form of ions; organic solvent is gradually volatilized through calefaction at 700 ℃, then the offspring is turned into BaTi5O11. With the temperature increasing to 850 ℃, BaTi5O11 begins resolving partly and forming BaTi4O9, and at 1000℃ Ba4Ti13O22 forms partly, but BaTi4O9 is the main crystal phase. BaTi5O11 and Ba4Ti13O30 decomposes completely at 1200℃ and forms single-phase BaTi4O9. The infrared (IR) analysis also shows that the absorbing peak of Ti-O bond is not in the characteristic absorption range of Ti-O-Ti (700-900 cm-1), but slightly shifted to the higher end (908 cm-1). It is probably because that doping Pr enters into the crystal lattice and causes the abnormal absorption of Ti-O bond.     

Dielectric tunable properties of BaTi_4O_9-doped Ba_(0.6)Sr_(0.4)TiO_3 microwave composite ceramics

BaTi4O9-doped Ba0.6Sr0.4TiO3 (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 Tm 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. Inter-estingly, 70 wt% BaTi4O9-doped BST has a tunability ~4.0% (under 30 kV/cm biasing) versus a permit- tivity ~68 and quality factor ~134.1 (at ~3.2 GHz).     

铁微量掺杂对二钛酸钡陶瓷介电性能的影响

采用常规固相反应法,以碳酸钡、二氧化钛和三氧化二铁为原料,制备微量铁掺杂的二钛酸钡陶瓷,研究了铁掺杂含量对二钛酸钡陶瓷的相纯度、相对密度和介电性能的影响.采用X射线粉末衍射仪检测二钛酸钡陶瓷的相成分,利用精密阻抗分析仪测量其介电性能.结果表明,微量铁元素进入了二钛酸钡晶格,能够获得单相二钛酸钡陶瓷的最大铁掺杂量在0.5%～1%之间.随着铁含量的增加,铁电相变居里温度快速减小,从未掺杂时的415 ℃降至铁含量为0.02%时的376 ℃和铁含量为0.5%时的324 ℃.同时介电常数逐渐减小,介电峰不断发生宽化,但并没有导致弛豫性铁电体的出现.微量铁元素的掺杂在实验测量误差范围内对陶瓷的密度影响不大.     

(Ba1-xPrx)Ti1-x/4O3陶瓷固溶度及位占据的研究

采用固相反应法制备了(Ba_1-xPr_x)Ti_1-x/4O₃（x = 0.10-0.20）（BPT）的陶瓷。由X射线衍射（XRD）和电子顺磁共振（EPR）技术研究了BPT陶瓷的固溶度及Pr离子的位占据情况。结果表明: BPT陶瓷的固溶度为x = 0.17,且在固溶限制范围内BPT具有单相立方钙钛矿结构;Pr离子支配性地占据Ba位。     

Ba3La2Ti2Ta2O15: A New Microwave Dielectric of A5B4O15-type Cation-deficient Perovskites

The synthesis, structure and properties of a new A5B4O15-type cation-deficient perovskite Ba3La2Ti2Ta2O15 were discribed. The compound was prepared by the conventional solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The results reveal that the compound is successfully synthesized. The compound crystallizes in the trigonal system with unit cell parameter a=5.6730(2) A, c=11.6511(2) A, V=324.93(1) A3 and Z=1. The microwave dielectric properties of the ceramic are studied using a network analyzer, and it shows a high dielectric constant of 45.1, a high quality factors with Q×f of 21029GHz, and a positive τf of 5.3ppm℃-1.     

Sr2Bi4-xLaxTi5O18铁电陶瓷性能的研究

采用固相烧结工艺制备了Sr2Bi4-xLaxTi5O18(x=0.00,0.10,0.25,0.50,0.75,1.00)陶瓷样品。用X射线衍射仪对其微结构进行了分析，并测量了其铁电、介电性能、。结果表明，随着La含量的增加，样品的剩余极化Pr和矫顽场Ec逐渐减小，这是由于La掺杂使得样品晶格畸变变小，从而导致剩余极化的降低。相变温度Tc随着La含量的增加而降低，这也与样品晶格畸变有关。     

SYNTHESIS AND CHARACTERIZATION OF A NEW NIOBATE: Sr6Ti7Nb9O42

A new niobate Sr_6Ti_7Nb_9O_(42) was synthesized for the first time by solid state reaction in SrO-TiO_2Nb_2O_5 ternary system. The new compound was characterized by EPMA, XRD, SEM and DTA. The X-ray owder diffraction data of Sr_6Ti_7Nb_9O_(42) were firstly reported in the paper. Sr_6Ti_7Nb_9O_(42) crystallizes the hexagonal system with unit cell parameters a=8.9991(4)(?), c=11.5118(9)(?), and space group P6_3/mcm(193), z=1. The calculated and measured densities are 4.783 g/cm~3 and 4.764 g/cm~3, respectively.     

BNT系纳米粉体的制备及微波特性研究

使用柠檬酸盐法成功制备出分散良好的颗粒状BNT系纳米粉体。经TEM和XRD分析,粉体的平均粒径约30 nm,其主晶相为Nd2Ti2O7,经1 300℃烧结成瓷后还出现了BaNd2Ti4O12相。此类材料具有良好的高频特性,用此类材料研制出的单片微波陶瓷电容器具有良好的微波特性。     

Ferroelectric properties of Bi_(3.25)La_(0.75)Ti_(3)O_(12) thin films prepared by sol-gel method

The Bi3.25La0.75Ti3O12 thin films were fabricated on the Pt/Ti/SiO2/Si substrates using sol-gel method. The structure and morphology of the films were characterized us-ing X-ray diffraction and atomic force microscopy. The thin films showed a perov- skite phase and dense microstructure. The 2Pr and 2Vc of the Bi3.25La0.75Ti3O12 thin films annealed at 700℃ were 18.6 μC/cm2 and 4.1 V, respectively, under an applied voltage 10 V. After the switching of 1×1010 cycles, the Pr value decreased to 90% of its pre-fatigue values. The films showed good insulating behavior according to the test of leakage current. The dielectric constant and the dissipation factor of the Bi3.25La0.75Ti3O12 thin films were about 176 and 0.046 at 1 kHz, respectively.     

Electric characteristics of Nd_2O_3 doped BaTiO_3 ceramics

0　INTRODUCTIONBaTiO3hasbeenextensivelystudiedandwidelyuti lizedasaceramicmaterialforelectronicapplications .TheuseofadditivespermitsvaryingoftheCurietemperatureandpresentsapeculiarvariationoftheresistancewithtemperature[1,2 ] .Commonadditivesaredopantionssuchasyttrium ,whichsubstituteforbariumandpromotean typesemiconductivity .Therare earthelementsinBa TiO3ceramicscouldlowertheresistivitiy ,improvethedi electriccharacteristicsanddecreasethesinteringtempera turenoticeably[3,4 ] ,sotheim…     

Bi4Ti3O12陶瓷及其A和B位掺杂的介电研究

测量了Bi4Ti3O12(BTO)陶瓷及其A和B位掺杂的系列材料介电损耗。在温度损耗谱上观察到一损耗峰，通过氧处理和内耗等相关实验手段，证实该峰（PI）是与氧空位有关的弛豫峰。同时观察该峰随不同掺杂类型的变化，分析了BTO陶瓷B位掺杂对铁电性的影响。     

Effect of La Doping on Microstructure and Ferroelectric Properties of Bi4Ti3O12 Thin Films Prepared by Sol-gel Method

The Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr (remanent polarization) value of Bi3.25La0.75Ti3O12 thin films is 18.6 Μc/cm2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.25La0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.     

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。     

溶胶-凝胶法制备（Nd,Bi）_4Ti_3O_（12）铁电薄膜

采用溶胶-凝胶法在Pt/Ti/SiO2/Si基片上制备了（Nd,Bi）4Ti3O12薄膜。将薄膜于空气中分别进行每1层、每2层、每3层500℃预退火10 min,最后于氮气氛中680℃退火30 min。结果表明：预退火工艺对薄膜的结构和铁电性能都有影响：每一层预退火处理的薄膜具有较大的剩余极化值和最小的矫顽场（2Pr=47.8μC/cm2,2Ec=254 kV/cm）。所有薄膜都呈现良好的抗疲劳特性。     

STRUCTURAL AND FERROELECTRIC PROPERTIES OF A NEW NIOBATE : Sr6FeNb9O30

A new niobate Sr_6FeNb_9O_(30) was synthesized in the ternary system SrO-Fe_2O_3-Nb_2O_5 for the first time. The crystal structure was determined by X-ray diffraction and dielectric measurement, and it belongs to orthorhombic tungsten bronze structure at room temperature with unit cell parameters a=1.7554(1) nm, b=1.7534 (1) nm, c=0.77870 (6) nm. Dielectric constants measurement show that Sr_6FeNb_9O_(30) has two phase transitions, paraelectric to ferroelectric at 185C and ferroelectric to ferroelastic at 70C.     

CCTO掺杂对BaTiO3-Nb2O5-Co3O4陶瓷系统介电性能的影响

以BaTiO3-Nb2O5-Co3O4(BTNC)系统陶瓷为研究对象,研究了掺杂CaCu3Ti4O12(CCTO)对该系统陶瓷介电性能的影响.结果表明,在20～85℃温度范围内,BT系统中CC-TO掺杂量为3.0%时,体系平均介电常数>2 600,温度稳定性△C/C≤4.7%;在20～125℃温度范围内,BTNC系统中CCTO掺杂量为2.0%时,体系的平均介电常数>2 700,温度稳定性△C/C≤10%;CCTO掺杂量为4.0%时,平均介电常数>2 200,温度稳定性△C/C≤4.7%.     

Small Rb~+ Doping in CaCu_3Ti_4O_(12)——A Possible Approach to Reduce Dielectric Loss

Ca1-xRbxCu3Ti4O12 （x=0, 0.01, 0.02 and 0.03） ceramics were synthesized by the sol-gel method. Doping Rb＋ reduces dielectric loss, which reaches minimum when x=0.02. By measuring properties of electrical conduction, larger leakage current density and height of grain-boundary Sehottky potential barrier （φB） were found in the doped samples, and φB became maximum when x=0.02. These results are attributed to the increase in the amount of oxygen vacancies and the formation of Cu-rich/Ti-poor grain-boundary layers, and it can be concluded that the dielectric loss in CCTO ceramic can be reduced by manipulating the composition and electrical properties of grain boundary.     

BaO-TiO2-Nd2O3-La2O3系陶瓷结构与介电性质研究

在BaO-TiO2-Nd2O3(BTN)系材料中以La2O3部分取代Nd2O3后构成BaO-TiO2-Nd2O3-La2O3(BTNL)系的结构和介电性能。实验结果证实,随着La2O3和Nd2O3摩尔比的增加,介电常数的温度系数((下降,用XRD分析证明是因为BaLa2Ti4O12和La2Ti2O7相的增加所致。在BTNL系中加入适量的添加剂可获得中温下烧结的具有超低损耗的微波陶瓷材料,可用于研制微波独石电容器。     

纳米絮状Li_4Ti_5O_(12)的水热法合成及性能的研究

为解决高温烧结制备的锂离子电池负极材料Li4Ti5O12易团聚、形貌差的问题,采用水热低温烧结法,以钛酸丁酯、氢氧化锂分别为钛源和锂源,异丙醇为溶剂,制备纯相Li4Ti5O12。用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和比表面测试仪对样品进行表征,采用恒流充放电法对钛酸锂进行电化学性能评价。结果表明,在400℃低温煅烧后可得到单一纯相尖晶石型Li4Ti5O12,所制备样品为具有大比表面积的纳米絮状粉体,表现出良好的电化学性能,在常温条件下,以0.1C倍率进行充放电,首次放电容量达到155.7mA·h/g,经50次循环后容量仍保持约143mA·h/g,容量保持率达到91.8%。     

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。