中低温烧结的温度稳定型Ba1-xCdxTiO3介电材料

温度稳定型钛酸钡基介电材料具有良好的性能,然而做为MLCs瓷料时,烧结温度偏高.用固溶体Ba_1-xCd_xTiO₃替代BaTiO₃做为基料,可以有效地降低烧结温度,制备符合X7R标准的MLCs瓷料,获得较高的室温介电常数.     

钛酸锆固溶体微波介电瓷的制备与性能

用共沉淀的方法制备了一系列ZrxTi1-xO4(0.4≤x≤0.6）纳米粉，XRD物相分析为ZrTiO4固溶体，TEM观察粒子粒径为20～30nm。通过制陶实验对该系列固溶体的烧结特性，形貌及介电性能进行了研究。结果表明，TiO2含量影响固溶体的最佳烧结温度，在相同的烧结温度下，TiO2含量越高，瓷体的相对密度越低，晶粒越大。该材料有很好的频率、温度稳定性，其介电性能与组成和瓷体的相对密度有关。介电常数和品质因数随瓷体相对密度增大而增大。当材料的相对密度高于90%时，随着TiO2含量增加，其介电常数增大，而品质因数降低。     

Ba0.65Sr0.35TiO3陶瓷材料的制备及介电特性研究

采用溶胶－凝胶工艺制备了Ba0.65Sr0.35TiO3粉体，并利用微波烧结技术对粉体进行了合成和烧结，研究分析了样品的介电特性，并与传统制备工艺获得的样品进行了性能比较。实验结果表明，获得的Ba0.65Sr0.35TiO3粉体颗粒较细，其合成温度和烧结成瓷温度都较传统工艺有大幅度降低，分别为900和1310℃；可以获得晶粒尺寸在1μm以内的陶瓷；随晶粒的减小，材料的相对介电常数变化不大，而介电损耗大大降低。     

半化学法制备0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3 陶瓷的研究

研究了制备纯钙钛矿相0．80Pb(Mg1／3Nb2／3)O3-0．20PbTiO3(缩写为PMNT)陶瓷的半化学法新工艺．详细讨论了除Nb2O5外，其它反应物以其非氧化物形态分别代替PbO、MgO和TiO2，以及PbTiO3或同成分的0．80PMN-0．20PT等钙钛矿相子晶对PMNT预烧粉体中钙钛矿相含量的影响；探讨了烧结温度对半化学法制备的PMNT陶瓷介电性能的影响，并对PMNT陶瓷的相组成、显微组织及介电性能进行了表征和测定．结果表明：提高镁组分的反应活性对提高预烧粉体中钙钛矿相含量的效果较好，同时以钛酸四丁酯取代TiO2的效果最好；半化学法工艺简单，能在850。C／2h预烧条件下制得几乎纯钙钛矿相的PMNT粉体，经过较低的烧结温度(950℃／2h)可制得致密的、介电性能优异的PMNT陶瓷．     

银掺杂对Bi2O3-ZnO-Nb2O5系陶瓷介电及熔融物性的影响

在BZN系陶瓷中，立方焦绿石结构的α相与低对称结构的β相是二个重要的基本物相，α相是熔点为1190℃的同成分熔融化合物，对应负温度系数，β相是转熔温度为1100℃的异成分熔融化合物，对应正温度系数，α相与β相按一定比例组成(α+β)复相瓷料，得到CH组零温度系数.分别在α相、β相以及CH组复相瓷料中进行银掺杂，通过瓷料介电性能的研究，首次明确了银掺杂对α相、β相以及CH组复相瓷料介电性能的不同影响和影响程度，进一步研究银掺杂β相瓷料的熔融物性，结果表明银掺杂对瓷料熔融物性的影响是影响其介电性能的内因.     

Ba0.65Sr0.35TiO3陶瓷材料的制备及介电特性研究

采用溶胶-凝胶工艺制备了Ba_0.65Sr_0.35TiO₃粉体,并利用微波烧结技术对粉体进行了合成和烧结,研究分析了样品的介电特性,并与传统制备工艺获得的样品进行了性能比较.实验结果表明,获得的Ba_0.65Sr_0.35TiO₃粉体颗粒较细,其合成温度和烧结成瓷温度都较传统工艺有大幅度降低,分别为900和1310℃;可以获得晶粒尺寸在1μm以内的陶瓷;随晶粒的减小,材料的相对介电常数变化不大,而介电损耗大大降低.     

BZT与CT复合微波陶瓷的结构和性能

采用预成瓷的方法,得到单斜类锆钙钛矿相Bi2(Zn1/3Ta2/3)2O7(β-BZT)和钙钛矿相CaTiO3(CT)的粉末,分别作为正负温度系数组元制备复相零温度系数微波陶瓷.预成瓷法可以抑制两相固溶反应,有效降低复相陶瓷烧结温度.采用复相方法可以调节温度系数,特别是在940℃烧结的CT含量为5%的样品,其介电常数εr=73.3(1MHz),温度系数αε=27×10-6/℃.     

Fe,Ni掺杂(Zr,Sn)TiO4陶瓷的结构和介电性能

用电子陶瓷工艺制备主晶相为（Zr,Sn)TiO4的介电陶瓷，（Zr,Sn)TiO4的结构和正产晶系，空间群Pbcn。研究用Fe,Ni掺杂对（Zr,Sn)TiO4陶瓷的介电性能的影响。铁掺杂降低了瓷料的烧结温度，同时减小了系统的Q值（Q＝1/tgδ），但在一定的范围内，随着Ni掺杂量的增大，Q值的下降被抑制，这可能是因为Ni离子阻碍了Fe离子扩散进入晶粒，使得Fe离子富集在晶界上，形成Fe-Ni尖晶石结构，减少了Fe对Q值的影响。     

SrTiO3独石化晶界层电容器研究

本文研究了低温烧结ＳｒＴｉＯ３晶界层瓷料系统中Ｂｉ２Ｏ３、Ｌｉ２Ｏ、ＳｉＯ２等掺杂剂对瓷料半导化及烧结特性的作用与影响，讨论了将这种瓷料应用于常规多层陶瓷电容器制作技术的工艺特点和技术关键。实验表明，利用晶界偏析技术制造ＳｒＴｉＯ３独石化晶界层电容器是一条可行性好的技术路线。     

PVB对玻璃/陶瓷流延生料带结构与烧结性能的影响

用聚乙烯醇缩丁醛作为配制硼硅酸盐玻璃/α-Al2O3流延浆料的粘结剂,流延成型制备玻璃/Al2O3生料带,研究了PVB对玻璃/Al2O3复合料生料带密度、力学性能、微观结构及其烧结性能等的影响。实验结果表明,随着PVB分子量和羟基含量减小,生料带拉伸强度和断裂伸长率降低、体积密度增加、生料带排胶热分解温度降低,对烧结瓷体密度和介电性能的影响较小。     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Interfacial microstructure of NiSix/HfO2/SiOx/Si gate stacks

Integration of NiSi_x based fully silicided metal gates with HfO₂ high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi_x film. Ni content varies near the NiSi/HfO_x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi_x/HfO₂ interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi_x/HfO_x was found higher than that of poly-Si/HfO₂, likely due to compositional non-uniformity of NiSi_x. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed.     

Tc trend in high-Tc superconductors

In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT _c enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT _c variation in members of the Tl₁ series of high-T _c superconductors. Our results indicate that an optimumT _c is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array.     

Anomalous Hall Effect in Sn1?x?yMnxEuyTe and Sn1?x?yMnxEryTe Mixed Crystals

The Anomalous Hall Effect (AHE) was investigated in IV–VI ferromagnetic semimagnetic semiconductors of Sn_1–x Mn _x Te codoped with either Eu or Er. The analysis of experimental data is as follows. Hall resistivity and magnetization showed that AHE coefficient R _s depends on temperature and its value decreases with thetemperature increase. We observe that above ferromagnet–paramagnet transition temperature R _s changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of R _s , particularly change of the sign.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.