用8—羟基喹啉（oxine）制备Ba（Mg1／3Ta2／3）O3粉体

本文对用８－羟基喹啉（ｏｘｉｎｅ）为螯合剂来制备Ｂａ（Ｍｇ１／３Ｔａ２／３）Ｏ３（ＢＭＴ）粉料进行了研究。就ｏｘｉｎｅ的加入量，ｐＨ值的改变对生成钽镁沉淀的产率及其粉料性能的影响进行了研究比较，结果表明，当ｏｘｉｎｅ的加入量大于ＭｇＴａ２Ｏ６摩尔数的３倍，ｐＨ值保持在１０左右时制得的钽镁粉较为理想，其比表面积达３２ｍ＾２／ｇ，与ＢａＣＯ３混合后烧结温度比用传统制备法降低１８０～２５０℃。     

B位离子共沉-煅烧法制备Ba(Mg1/3Ta2/3)O3微波陶瓷材料

采用钽镁共沉淀法制备ＭｇＴａ２Ｏ６粉体,然后与ＢａＣＯ粉体混合制备Ｂａ（Ｍｇ１／３Ｔａ２／３）Ｏ３（简称ＢＭＴ）微波陶瓷材料,成功地解决了ＴａＣｌ３溶解问题。对钽镁共沉条件和粉体热分解工艺与粉体的平均粒径和钽镁比例关系;ＢＭＴ陶瓷制备工艺与材料的微观结构和微波性能关系进行了研究,制备的ＭｇＴａ２Ｏ６晶相粉体平均粒径为０．３μｍ,最大与最小粒径比为５。制备的ＢＭＴ陶瓷的几乎不含ＢａＴａ２Ｏ６等杂相,     

MnO2对0.85Pb（Zn1／3Nb2／3）O3—0.15BaTiO3陶瓷弛豫现象的影响

研究了ＭｎＯ２掺杂对０．８５Ｐｂ（Ｚｎ１／３Ｎｂ２／３）Ｏ３－０．１５ＢａＴｉＯ３陶瓷电介电、热释电以及铁电弛豫等性能的影响。添加ＭｎＯ２使ＰＺＮ－ＢＴ陶瓷的介电常数ε下降，室温老化率明显增大。随着ＭｎＯ２含量的增加，ＰＺＮ－ＢＴ陶瓷介电常数与温度的关系中所表现出来的频率弛豫现象逐渐减弱，直到消失，但其扩散相变现象仍然十分明显。     

烧成制度及杂质对Mg—PSZ材料极出体形态和力学性能的影响

以阳泉产ＺｒＯ２原料为研究对象，通过控制烧成制度，即在烧结温度前保温（１６００℃），再在Ｃ相区烧结固溶，经慢速至１１００℃后再自然冷却到室温，可使基体中长出大小合适的析出体，获得较佳的力学性能，含１０ｍｏｌ％ＭｇＯ的Ｍｇ－ＰＳＺ材料强度 可ａ韧 可达１２．３ＭＰａ·ｍ＾１／２，与宜兴料相比较，可知步量杂质（Ｆｅ２Ｏ３）可略降低材料的烧结温度，但对材料的力学性能无影响，通过ＳＥＭ对选用不同烧成制度材     

湿化学法制备0．95Pb（Mg_（1／3）Nb_（2／3））O_3－0．05PbTiO_3铁电陶瓷

用湿化学法制备了钙钛矿相的含量为９９％的０．９５Ｐｂ（Ｍｇ＿（１／３）Ｎｂ＿（２／３））Ｏ３－０．０５ＰｂＴｉＯ＿３（简称０．９５ＰＭＮ－０．０５ＰＴ）微粉，ＳＥＭ显示其粒度为０．２～０．３μｍ。通过ＸＲＤ确定了合成０．９５ＰＭＮ－０．０５ＰＴ前驱物的最佳条件为：溶液的ｐＨ值为１．５，反应温度为６０℃。制备０．９５ＰＭＮ－０．０５ＰＴ陶瓷时，预烧温度为８００℃（２ｈ），烧结温度为１２５０℃（１ｈ）。粉末烧结后制得纯钙钛矿相的０．９５ＰＭＮ－０．０５ＰＴ铁电陶瓷，其密度为理论密度的９５％，介电常数为１４８００（８００Ｈｚ）。     

湿化学法制备0.95Pb（Mg1／3Nb2／3）O3—0.05PbTiO3铁电陶瓷

用湿化学法制备了钙钛矿相的含量为９９％的０．９５Ｐｂ（Ｍｇ１／３Ｎｂ２／３）Ｏ３－０．０５ＰｂＴｉＯ３确定了０．９５ＰＭＮ－０．０５ＰＴ前驱物的最佳条件为：溶液的ｐＨ值 为１．５，反应温度为６０℃。     

MgO,Y2O3添加剂对原位反应制备ZTM／Al2O3材料性能的影响

本文主要探讨了ＭｇＯ、Ｙ２Ｏ３添加剂对原位反应制备ＺＴＭ／Ａｌ２Ｏ３材料常温力学性能的影响。实验表明：ＭｇＯ可明显提高材料的烧结致密度;Ａｌ２Ｏ３的含量越高,ＭｇＯ的添加越有利于材料常温抗弯强度的提高;ＭｇＯ对材料韧性的贡献小于Ｙ２Ｏ３;Ｙ２Ｏ３可明显改善材料的韧性,地常温抗弯强度的提高作用不大;对烧结致密化的作用小于ＭｇＯ。Ｙ２Ｏ３改善材料韧性的原因是与ＺｒＯ２形成固溶体。     

Cr_2O_3在SiO_2-Al_2O_3-MgO-B_2O_3系玻璃和玻璃陶瓷中的作用

利用ＳＭＥ和ＸＲＤ等技术,系统研究了Ｃｒ２Ｏ３对ＳｉＯ２－Ａｌ２Ｏ３－ＭｇＯ－Ｂ２Ｏ３系玻璃和玻璃陶瓷中的作用。当Ｃｒ２Ｏ３％＜１时,随着Ｃｒ２Ｏ３。含量的增加,玻璃试样的颜色由浅绿色逐渐转变成灰色;Ｃｒ２Ｏ３％＞１时,镁铬（铝）类晶石,Ｍｇ（Ａｌ１．５Ｃｒ０．５）Ｏ４,在玻璃试样中析出;在玻璃陶瓷中,Ｃｒ２Ｏ３％的含量的增加有助于Ｍｇ（Ａｌ１．５Ｃｒ０．５）Ｏ４相的析出,对云母晶体的析出有抑制作用。同时还发现Ｃｒ２Ｏ３的含量对云母晶体显微组织也有显著的影响作用。     

正丁醇钛—乙酸钡水解法合成BaTiO3粉体的研究

本文着重研究了Ｔｉ（Ｏ＾ｎＢａ）４－Ｂａ（ＤＡｃ）２水解法合成高纯超细ＢａＴｉＯ３粉体的制备工艺。借助ＴＧＤＴＡ，ＸＲＤ，ＴＥＭ，ＳＥＭ，ＳＡＸＳ和ＩＣＰ－ＡＥＳ等分析手段，研究了ＰＨ值，Ｂａ／Ｔｉ比和（Ｂａ／Ｔｉ）比，反应温度，浸泡处理等对ＢａＴｉＯ２粉体性能的影响，采用本工艺方法合成的ＢａＴｉＯ３粉体，纯度达９９．８０ｗｔ％，比表面积为６８ｍ＾２／ｇ，一次粒子平均粒径４６．７ｎｍ，二次粒子粒径     

新型NZP族磷酸盐陶瓷Ca1-xBaxZr4(PO4)6的合成及其性能研究

用共沉淀法合成了Ｃａ１－ｘＢａｘＺｒ４（ＰＯ４）６（０〈ｘ〈１）系列ＮＺＰ族陶瓷的粉体,添加３ｗｔ％的ＭｇＯ,在５０～１００ＭＰａ下干压成型,分别在１３００℃下无压烧结１～２ｈ,制成ＣＢＺＰ系列陶瓷材料。对这些材料分别进行太强度测试,用扫描电镜观察了显微结构,测定了室温１０００℃的平均线膨胀系数。其中ＣａＺｒ４（ＰＯ４）６（ｘ＝０）和ＢａＺｒ４（ＰＯ４）６（ｘ＝１）的抗压强度分别达１５７．４ＭＰａ     

Ferroelectric Ceramics in the PbMg1/3Nb2/3O3-PbCd1/3Nb2/3O3 System

Solid solutions (1-x)PbMg_1/3Nb_2/3O₃ + xPbCd_1/3Nb_2/3O₃ with x = 0-0.30 are investigated with purpose to work out a capacitor ceramics with good dielectric properties and low sintering temperature. It is found that the perovskite phase forms at sintering near to 980°C and begins to decompose at higher temperatures. When x grows from 0 to 0.30, the Curie temperature linearly grows from -10°C to +25°C, the dielectric permittivity ε_m in the Curie point T_C decreases from 18000 to 6800 and the phase transition becomes more diffused. The dielectric permittivity at room temperature is rather high and the temperature stability is improved. The system is of interest, because it can serve as a base for working out some ceramic materials for capacitors with low sintering temperature, which needs of no special atmosphere at burning.     

Structure Evolution from Pb(Mg1/3Nb2/3)O3 to La(Mg2/3Nb1/3)O3

The crystal structure of lanthanum-modified lead magnesium niobates having composition (Pb_{1− x} La _x ) (Mg_{(1+ x )/3}-Nb_{(2− x )/3})O₃ with X = 0 to 1 was investigated by X-ray powder diffraction. It was found that the fundamental reflections from perovskite structure remain in the whole range of composition. The superlattice reflections from the A(B'_1/2-B"_1/2)O₃ ordered structure are also well preserved for La content greater than 50 at.%; however, a series of extra peaks of mixing indices appears, with intensities gradually enhanced with the increase of La content. For the complete substitution of Pb by La, a splitting of some reflections can be observed in the diffraction pattern. The results indicate that the crystal structure evolves continuously with the La content, from disordered cubic perovskite of space group Pm 3 m for X = 0, to ordered cubic perovskite of space group Fm 3 m for X = 0.5, distorted cubic perovskite of space group Pa 3 for 0.5 < X < 0.9, and finally to a rhombohedral perovskite, possibly belonging to the space group R 3 , for X ≥ 0.9. In the evolution of structure, a linear reduction of the lattice constant of the perovskite cell from 4.048 to 3.964 Å was observed.     

Morphotropic Phase Boundary in the Pb(Zn1/3Nb2/3O3)-BaTiO3-PbTiO3 System

The morphotropic phase boundary (MPB) in the relaxor ferroelectric system Pb(Zn_1/3Nb_2/3O₃)-BaTiO₃-PbTiO₃ (PZN-BT-PT) with 15 mol% BT was investigated through dielectric permittivity and high-temperature X-ray diffraction measurements. It was revealed that MPB is a broad composition region extending from 12 to 18 mol% PT, within which the temperatures of the permittivity maximum are close to the ending temperatures for the phase transformation from coexisting rhombohedral and tetragonal phases to cubic phase on heating. When the specimen is cooled, the starting temperatures for the rhombohedral-to-tetragonal phase transition increase with increasing PT content. The large thermal hysteresis observed by X-ray diffraction is caused by the phase transformation between rhombohedral and tetragonal phases. On cooling, the MPB curves toward the PT-rich side, so that ceramics within this composition range undergoe successive phase transitions from cubic to rhombohedral and from rhombohedral to tetragonal phase. The diffuseness of the paraelectric-to-ferroelectric phase transition is remarkably decreased by the addition of PT. The enhanced dielectric permittivity peak values for the MPB compositions are correlated with the reduced lattice distortion and phase coexistence.     

Sintering of glass-added BaZn1/3Nb2/3O3 ceramics

The complex perovskite oxide Ba(Zn_1/3Nb_2/3)O₃ (BZN) has been studied for its attractive dielectric properties which place this material interesting for applications as multilayer ceramics capacitors or hyperfrequency resonators. This material is sinterable at low temperature with combined glass phase–lithium salt additions, and exhibits, at 1 MHz very low dielectric losses combined with relatively high dielectric constant and a good stability of this later versus temperature. The 2 wt.% of ZnO–SiO₂–B₂O₃ glass phase and 1 wt.% of LiF-added BZN sample sintered at 900 °C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant ?_r of 39, low dielectrics losses (tan(δ) < 10⁻³) and a temperature coefficient of permittivity τ_? of 45 ppm/°C⁻¹. The 2 wt.% ZnO–SiO₂–B₂O₃ glass phase and 1 wt.% of B₂O₃-added BZN sintered at 930 °C exhibits also attractive dielectric properties (?_r = 38, tan(δ) < 10⁻³) and it is more interesting in terms of temperature coefficient of the permittivity (τ_? = −5 ppm/°C). Their good dielectric properties and their compatibility with Ag electrodes, make these ceramics suitable for L.T.C.C applications.     

Cation Ordering Transformations in the Ba(Zn1/3Nb2/3)O3-La(Zn2/3Nb1/3)O3 System

Single-phase perovskites were formed in the (1−_x)Ba(Zn_1/3Nb_2/3)O₃-( _x )La(Zn_2/3Nb_1/3)O₃ system for compositions with 0.0≤ x ≤0.6. Although the stability of the trigonal "1:2" ordered structure of the Ba(Zn_1/3Nb_2/3)O₃ end member is very limited (0.0≤ x ≤0.05), low levels of lanthanum induce a transformation to a cubic, "1:1" ordered structure that has a broad range of homogeneity (0.05≤ x ≤0.6). Samples with x > 0.6 were comprised of La₃NbO₇, ZnO, and a perovskite with x = 0.6. The cubic 1:1 phases were fully ordered and no evidence was found for a compositionally segregated microstructure. These observations could not be reconciled in terms of a "space-charge" model; rather, they supported a charge-balanced, "random-site" structure for the 1:1 cation-ordered Ba(β_1/2'β_1/2")O₃ phases.     

Sintering Behavior and Surface Microstructure of PbO-Rich PbNi1/3Nb2/3O3–PbTiO3–PbZrO3 Ceramics

The sintering behavior and surface microstructure of PbNi_1/3Nb_2/3O₃–PbTiO₃–PbZrO₃ (PNiNb-PT-PZ) ceramics were investigated. The PNiNb-PT-PZ ceramics with the stoichiometric composition and the addition of excess lead oxide (PbO-rich ceramics) were sintered by liquid-phase sintering in accordance with the solution-reprecipitation mechanism at temperatures below the melting point of PbO. The temperature at which the liquid phase forms fell to near the eutectic point of the PbO–Nb₂O₅ and the PbO–TiO₂ system (868°C) with the addition of 5 mol% PbO. As the calcination temperature influenced the sinterability of the stoichiometric PNiNb-PT-PZ ceramic, unreacted PbO was considered to be the source of the liquid phase in the sintering of the stoichiometric powder. The secondary phase was observed at the surface of PbO-rich ceramics and was suggested to be a liquid phase expelled from inside the ceramic. A sintering scheme of PNiNb-PT-PZ ceramics was proposed, and the high sinterability of PNiNb-PT-PZ ceramics was attributed to the low formation temperature of the liquid phase.     

Effect of the hydrogen spillover on the selectivity of dibenzothiophene hydrodesulfurization over CoSx/γ-Al2O3, NiSx/γ-Al2O3 and MoS2/γ-Al2O3 catalysts

Dibenzothiophene (DBT) hydrodesulphurization (HDS) reaction at 3 MPa and 325–375 °C on Mo/γ-Al₂O₃ single-bed and Me/γ-Al₂O₃//SiO₂//Mo/γ-Al₂O₃ (Me = Co or Ni) double-bed catalysts were investigated. Results indicate that ratio cyclohexylbenzene (CHB)/biphenyl (BP) or selectivity is higher when using double-beds rather than a single-bed. Synergy in dibenzothiophene hydrodesulphurization on Co//Mo and Ni//Mo double-beds is also detected. Changes in selectivity and conversion are attributed to the action of spillover hydrogen (Hso) formed in the first bed that reaches the second bed.     

Dielectric and Piezoelectric Properties of Pb(Co1/3Nb2/3)O3-PbTiO3-PbZrO3 Solid Solution Ceramics

Ceramic and piezoelectric properties of the Pb(Co_1/3Nb_2/3)O₃-PbTiO₃-PbZrO₃ system were investigated. The system contains rhombohedral, tetragonal, and pseudocubic phases at room temperature. The triple point is at 0.07Pb(Co_1/3Nb_2/3)O₃-0.43PbTiO₃-0.50PbZrO₃. High dielectric constants (750 to 1500) and radial coupling coefficients (40 to 45%) and low average temperature coefficients of resonant frequency (of the order of 10^-6°C) were obtained for compositions near the morphotropic phase boundary.     

Electromechanical Testing and Modeling of a Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 Relaxor Ferroelectric

Compressive prestress effects on the electrical and mechanical properties of relaxor ferroelectric materials were studied as a function of temperature for several formulations of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃-BaTiO₃ (PMN-PT-BT) ceramics. Experimentally measured polarization and strain, induced by an ac electric field, decreased as compressive stress increased. Effective Young's moduli also were measured under constant dc electric fields. A significant decrease in modulus was observed with increasing field. The prestress and modulus experiments were modeled analytically using a proposed relaxor ferroelectric constitutive law. In general, excellent agreement between the model and experiments was obtained, indicating that the model accurately predicted the coupled behavior of this relaxor ferroelectric material.     

Low-Temperature Synthesis of 0.65 PbMg1/3Nb2/3O3–0.35PbTiO3 Ceramics

Nanocrystalline 0.65 PbMg_1/3Nb_2/3O₃–0.35PbTiO₃ powders were synthesized by citrate gel method. The gel was prepared using citrate (titanium and niobium) and nitrate (lead and magnesium) salts. The hard gel obtained after completion of the reaction was treated to get the desired phase. Thermal analysis of the gel was done to optimize the calcination temperature. The calcined powders were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The crystallite size and the effective strain were found to be 50 nm and 0.03584 N, respectively.