Bi4Ti3O12掺杂中温烧结(Ba,Sr)TiO3基电容器陶瓷

研究了Bi4Ti3O12掺杂量(≥8%,质量分数)对(Ba,Sr)TiO3(Barium Strontium Titanate,BST)铁电电容器陶瓷介电性能的影响,得到不同Bi4Ti3O12掺杂量与BST陶瓷性能的关系,得到中温烧结(≤1150℃)、高压(≥6.99MV/m)、低损耗(0.008)、符合X7R特性的多层陶瓷电容器瓷料.借助扫描电镜(SEM)研究了Bi4Ti3O12对BST陶瓷微观结构的影响,探讨了Bi4Ti3O12掺杂量对BST陶瓷性能和结构影响机理.结果表明Bi4Ti3O12是通过与BST形成核-壳结构、形成玻璃相、偏析晶界及抑制晶粒生长、改善介温特性等来影响瓷料性能和结构的.这些结果为Bi4Ti3O12掺杂改性BST电容器陶瓷提供一定的依据.     

Bi3+离子取代对Ba6-3xLn8+2xTi18O54陶瓷结构与微波介电性能的影响

研究了Bi3+取代Ln3+对Ba6-3xLn8+2XTi18O54(LnSm,Nd)固溶体陶瓷的结构与微波介电性能的影响规律.对于Ba4[(Sm1-yNdy)1-zBiz]9 33Ti18O54,Bi3+取代对晶粒生长有促进作用,且使介电常数提高,但使Q·f值降低.xRD分析表明,对于y=0.2,当Bi3+的取代量z≤0.06时,材料保持类钙钛矿钨青铜单相结构,而当取代量较多时,类钙钛矿结构失稳,转变为(BiSm)2TiO7第二相,而对于y=0.7,则在Bi取代量达0.20时仍能保持单相钨青铜结构.且当z=0.10时,可获得优化的介电性能为ε=90.2,Q·f=9090GHz,τf=8.7×10-6/℃.     

Bi4Ti3O12掺杂中温烧结(Ba,Sr)TiO3基电容器陶瓷

研究了Bi4Ti3O12掺杂量(≥8%,质量分数)对(Ba,Sr)TiO3(Barium Strontium Titanate,BST)铁电电容器陶瓷介电性能的影响,得到不同Bi4Ti3O12掺杂量与BST陶瓷性能的关系,得到中温烧结(≤1150℃)、高压(≥6.99MV/m)、低损耗(0.008)、符合X7R特性的多层陶瓷电容器瓷料.借助扫描电镜(SEM)研究了Bi4Ti3O12对BST陶瓷微观结构的影响,探讨了Bi4Ti3O12掺杂量对BST陶瓷性能和结构影响机理.结果表明:Bi4Ti3O12是通过与BST形成核-壳结构、形成玻璃相、偏析晶界及抑制晶粒生长、改善介温特性等来影响瓷料性能和结构的.这些结果为Bi4Ti3O12掺杂改性BST电容器陶瓷提供一定的依据.     

富钛BaO-TiO2(Ti/Ba=4～4.5)系微波介质陶瓷

采用固相反应法制备了富钛BaTi4+xO9+2x(x=0.0-0.50)微波介质陶瓷,探讨了TiO2含量以及烧结温度对物相组成和介电性能的影响.在1300～1350 ℃烧结BaTi4+xO9+2x陶瓷即可达到约98%的相对密度.当x≤0.28时,BaTi4+xO9+2x陶瓷为BaTi4O9单相.随TiO2含量的增加,BaTi4+xO9+2x陶瓷从BaTi4O9单相逐渐转变成以BaTi4O9为主相,同时出现TiO2和Ba2Ti9O20相,并且随烧结温度提高,TiO2含量较多的试样中出现更多的Ba2Ti9O20相.随TiO2含量的增加介电常数逐渐增大,而Qf值呈下降趋势.Qf值从x=0.0时的约40 000 GHz逐渐降低至x=0.50时的15 000 GHz.     

钛钽镁酸钡的合成及其微波介电性

以Ba(Mg1/3Ta2/3)O3为基,通过不同量的Ti取代实验,探讨Ti取代对Ba(Mgx/12Ta2x/12Ti12-x/12)O3瓷(1/3＜x＜4=(简称BMTT)介电性能和结构的影响.结果表明Ti4+与Mg2+,Ta5+离子对构成类质同相代换,形成Ba(Mgx/12Ta2x/12Ti12-3x/12)O3(1/3≤x≤4)系列新固溶体,与Ba(Mg1/3T2/3)O3具有相同的晶体结构.当体系组成蜝a(Mg1/6Ta1/3Ti1/2)O3时,在1480℃下烧结保温3h所制备的材料微波介电性能为εr=89,Q×f=12 700GHz(6GHz下),τf=1.9×10-4/℃.     

BaTiO3-La2O3-MgO陶瓷微观结构与介电性能

采用传统固相反应法对水热BaTiO3粉体进行La2O3和MgO复合掺杂改性.研究(Ba1-xLax)(Ti1.x/2Mgx/2)O3体系的烧结性能、相组成、微观结构及介电性能.研究结果表明随着掺量x的增加,烧结温度提高,晶体结构逐渐由四方相转为立方相.当x=0.0025时,以Mg2+固溶取代Ti4+位占优势,晶格常数增加;当x≥0.2时,La3+固溶取代Ba位占优势,晶格常数下降.随着掺量的增加,晶粒尺寸减小.x=0.4时,平均晶粒尺寸约为0.33 μm,晶粒大小均匀,材料致密.随着掺量的增加,居里温度下降,居里峰展宽,电阻率提高.高掺量情况下(x≥0.2),随着掺量的增加,介电常数增加,介电常数随温度的变化率降低.BaTiO3-La2O3-MgO体系材料可以作为介电特性较为稳定、小尺寸、大容量的片式陶瓷电容器的介质材料.     

BaTiO3-La2O3-MgO陶瓷微观结构与介电性能

采用传统固相反应法对水热BaTiO3粉体进行La2O3和MgO复合掺杂改性.研究(Ba1-xLax)(Ti1.x/2Mgx/2)O3体系的烧结性能、相组成、微观结构及介电性能.研究结果表明:随着掺量x的增加,烧结温度提高,晶体结构逐渐由四方相转为立方相.当x=0.0025时,以Mg2+固溶取代Ti4+位占优势,晶格常数增加;当x≥0.2时,La3+固溶取代Ba位占优势,晶格常数下降.随着掺量的增加,晶粒尺寸减小.x=0.4时,平均晶粒尺寸约为0.33 μm,晶粒大小均匀,材料致密.随着掺量的增加,居里温度下降,居里峰展宽,电阻率提高.高掺量情况下(x≥0.2),随着掺量的增加,介电常数增加,介电常数随温度的变化率降低.BaTiO3-La2O3-MgO体系材料可以作为介电特性较为稳定、小尺寸、大容量的片式陶瓷电容器的介质材料.     

CuO掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的研究

用传统固相反应法在不同温度下烧结制备了不同含量CuO掺杂的0.45(Ba0.7Ca0.3)TiO3-0.55Ba(Zr0.2Ti0.8)O3(BCZT45)无铅压电陶瓷,研究了CuO掺杂对BCZT45陶瓷微观形貌、相结构、介电和压电性能的影响。X射线衍射(XRD)结果表明所有陶瓷均形成了钙钛矿结构,Cu2+固溶进入BCZT45晶格,Cu2+部分取代Ti4+引起晶格畸变。加入CuO改善了BCZT45陶瓷的烧结性能,降低了烧结温度,使陶瓷在1350℃即可烧结,提高了陶瓷密度。随着CuO含量的增加,陶瓷的介温曲线向低温方向移动。掺杂少量CuO后,BCZT45陶瓷的压电常数增大,随着CuO掺杂量的增加又急剧降低。掺杂CuO含量为0.25mol%的BCZT45陶瓷具有最好的电学性能:压电常数d33=340pC/N,室温介电常数εr=3147,介电损耗tanδ=0.025。     

La2O3添加剂对BST陶瓷介电性能的影响

钛酸锶钡(Ba1-xSrxTiO3)优异的介电性能使其在微波可调器件的应用中成为热门材料.以BaCO3,SrCO3和TiO2为原料,采用传统的固相合成方法制备了Ba0.6Sr0.4TiO3粉体,以La2O3为添加剂在1400℃烧结成钛酸锶钡陶瓷.分析了La2O3添加剂对陶瓷的微观形貌、相组成以及介电性能的影响.XRD分析表明La2O3能完全固溶到钛酸锶钡晶格中.掺杂后的陶瓷晶粒尺寸明显降低.掺杂了La2O3的钛酸锶钡的介电可调性有所增高.     

氧化铝掺杂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3陶瓷介电性能的影响

Zr4+取代Ti4+的Ba0.6Sr0.4(Zr0.2Ti0.8)O3固溶体在降低介电常数的同时,保持了BST固溶体优异的可调性。为降低BST材料的介电损耗和介电常数,以氧化铝为改性剂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3材料(BSZT材料)进行了掺杂。随着氧化铝掺杂质量分数从1%到10%增加,BSZT材料的介电常数从5000降低到了1550(100kHz),介电损耗降低到0.001(100kHz)以下,而材料的介电可调性保持在35%左右(1.5kV/mm)。X射线衍射图谱表明,烧结后得到的BSZT材料具有典型的钙钛矿结构。扫描电子显微镜观察表明,氧化铝的掺杂使得陶瓷致密度较高,晶粒均匀。     

V掺杂对Bi_(3.25)La_(0.75)Ti_3O_(12)层状结构铁电陶瓷电性能的影响

用高温固相烧结法制备了V~(5+)掺杂的Bi_3.25La_0.75Ti_3O_(12)(BLT)层状结构铁电陶瓷.利用XRD对Bi_3.25La_0.75Ti_(3-x)VxO_(12+x/2)(BLTV-x)材料结构进行了晶相分析,结果表明所制备的陶瓷均具有单一的正交相结构.样品的介电常数温度谱显示:V~(5+)掺杂提高了材料的介电常数,x=0.03时介电常数最大,但样品的居里温度并没有发生大的变化.样品的介电损耗谱表明:由于V~(5+)掺入,由氧空位引起的样品介电损耗被极大的压制,在x=0.06时损耗最小.通过对材料的直流电导与温度关系的Arrhenius拟合,分析了样品的导电机理,结果显示V~(5+)的掺杂大大降低了材料中氧空位的浓度,使得陶瓷样品的电性能得到了很好的改善.     

Low-field magnetoresistance of (1-x)La_(0.6)Dy_(0.1)Sr_(0.3)MnO_3/0.5x (Sb_2O_3) composite system under different sintering temperatures of matrix

A series of (1-x)La0.6Dy0.1Sr0.3MnO3/0.5x(Sb2O3)(x=0.15) samples were prepared by the solid-state reaction method, and the influence of sintering temperature of the matrix on low-field magnetoresistance of (1-x)La0.6Dy0.1Sr0.3MnO3/0.5x (Sb2O3) was studied through the measurements of X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) image, resistivity-temperature (ρ-T) curves, and magnetoresistance-temperature (MR-T) curves. The results indicate that for the samples with low sintering temp...     

Microstructure and electrical properties of Ti-modified (Na_(0.5)K_(0.5))(Ti_xNb_(1-x))O_3 lead-free piezoelectric ceramics

Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the lead-free NKNT ceramics were investigated. X-ray diffraction re-sults indicated that Ti4+ had diffused into the (Na0.5K0.5)NbO3 lattices to form a solid solution with a perovskite structure. The introducing of Ti into the (Na0.5K0.5)NbO3 solid solution effectively reduced the sintering temperature and...     

Optimization of dielectric constant temperature coefficient of pyrochlores containing bismuth

1　INTRODUCTIONDielectric ceramics are widely used with ad vances in microelectronic technologies. Bismuth based pyrochlores exhibit well known high fre quency dielectric properties for multilayer capaci tor. Group of pyrochlore structured compounds isof general formula A2B2O7(where A is trivalent orbivalent cations and B is quadrivalent and quinque valent cations). As a member of the pyrochlorefamily of compound, bismuth zinc niobate is a typi cal high frequenc…     

SrCO_3掺杂La_2Ti_2O_7陶瓷的电性能

通过固相反应合成法制备了La_2Ti_2O_7陶瓷,研究了SrCO_3掺杂对La_2Ti_2O_7陶瓷的电学性能的影响,并对导电机理做了初步的探讨分析.实验表明,随着Sr量的增加,电导激活能有下降的趋势,导致材料的电导率增加.在100 Hz～10 MHz频率下未掺杂Sr和掺杂量为x=0.01试样的介电常数分别为46和67,介电损耗都在1×10~(-3)数量级,说明这种材料具有较好的介电性能.     

Structure and electrical properties of (1-x)BaTiO_3+(x)La_(2/3)-Sr_(1/3)MnO_3 composites

Liquid-phase sintering method was used to prepare BaTiO 3 powders and the structure and electrical properties of (1-x)BaTiO 3 +(x)La 2/3 Sr 1/3 MnO 3 (LSMO) composites were investigated. The results of X-ray diffraction showed that the prepared BaTiO 3 powders were pure and fine, indicating that sintering temperature was effectively lowered when the NaCl sintering aid was added. X-ray diffraction patterns of (1-x)BaTiO 3 +(x)La 2/3 Sr 1/3 MnO 3 (LSMO) composites showed that LSMO and BaTiO 3 phases were coex...     

Piezoelectric and dielectric properties of Lix（K0.46Na0.54） 1-xNb0.86Ta0.1 Sb0.04O3 lead-free ceramics

Lead-free piezoelectric ceramics Lix（K0.46Na0.54）1-xNb0.86Ta0.1Sb0.0403 （with x ranging from 0 to 0.1） were synthesized by conventional solid state sintering method. The effect of cationic substitution of Li for K and Na in the A sites of perovskite lattice on the structure, phase transition behavior and electrical properties were investigated. Morphotropic phase boundaries（MPB） between orthorhombic and tetragonal phase are found in the composition range of 0.06≤x≤0.08. Analogous to Pb（Zr, Ti）O3, the dielectric and piezoelectric properties are enhanced for the composition near the morphotropic phase boundary. The Li0.06（K0.46Na0.54）0.94- Nb0.86Ta0.1Sb0.04O3 ceramics show excellent electrical properties, that is, piezoelectric constant d33=215 pC/N, planar electromechanical coupling factor kp=41%, dielectric constant ε33^T /ε0=1 303, and dielectric loss tan δ=2.45%. The results indicate that Lix（K0.46Na0.54）1 -xNb0.86Ta0.1Sb0.0403 ceramic is a promising lead-free piezoelectric material.     

Thermoelectric properties of Bi_（1.5）Pb_（0.5）Sr_（2-x）La_xCo_2O_y polycrystalline materials

Polycrystalline samples of Bi 1.5 Pb 0.5 Sr 2-x La x Co 2 O y (x = 0.1, 0.2, 0.3) with a layered structure were prepared by solid-state reaction method. All samples are p-type semiconductors. The thermoelectric properties, namely, the electric resistivity (ρ), Seebeck coefficient (S), and power factor (S 2 /ρ) of the samples are dependent on chemical composition. The values of ρ, S, and S 2 /ρ increase with an increase in temperature for all samples. The substitution of Pb 2+ for Bi 3+ and La 3+ for Sr 2+ improves the thermoelectric properties of the Bi 2 Sr 2 Co 2 O y system owing to the simultaneous decrease of electric resistivity and increase of Seebeck coefficient. As a result, the optimal thermoelectric property has been obtained in Bi 1.5 Pb 0.5 Sr 1.7 La 0.3 Co 2 O y and the power factor can reach 2.1 × 10-4 W·m-1 K-2 at 998 K.     

Gd3+掺杂La2Mo2O9的相稳定性及热导率

La2Mo2O9具有极低的热导率,但其在580℃左右会发生α-β相变,严重影响其性能和应用。本实验以Gd203掺杂La2Mo2O9制备了一系列La2-xGdxMo2O9 (x=0.0~0.5)固溶体,研究了掺杂Gd3+对La2Mo2O9相稳定性和热导率的影响。结果表明,随着Gd3+掺杂量的增加,相变得到有效抑制,当x≥0.2时样品以β相存在。样品的热导率随Gd3+掺杂量的增加先减小后增加,室温下在x=0.2时达到最低,此后缓慢上升,但所有样品的热导率均小于1 W/(m·K)。     

添加玻璃料对BaSm_2Ti_4O_(12)微波介质陶瓷烧结行为和介电性能的影响

利用固相法制备BaSm_2Ti_4O_(12)(BST)微波介质陶瓷.研究了复合添加Li_2CO_3-B_2O_3-SiO_2-CaO-Al_2O_3(LBSCA)和BaO-B_2O_3-SiO_2(BBS) 玻璃料对BaSm_2Ti_4O_(12)微波介质陶瓷的烧结性能、介电性能、相组成和微观结构的影响.研究表明:复合掺杂10% LBSCA和2%～5% BBS可使烧结温度降至900 ℃.XRD分析表明复合掺杂两种玻璃料的BST陶瓷主晶相为BaSm_2Ti_4O_(12)相,玻璃料以玻璃相的形式存在陶瓷晶粒间.复合掺杂10% LBSCA+3%BBS玻璃料的BST陶瓷可在900 ℃、保温2 h条件下烧结致密,微波介电性能为:ε_r =55.63,Q_f = 4266 GHz,τ_f= -13.5×10~(-6)℃~(-1),这种陶瓷材料有望与纯Ag电极共烧,制作各种多层微波频率元器件.