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。     

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）。     

影响（Ba_（0．65）Pb_（0．35））TiO_3系PTC陶瓷电阻率的因素

在合成的（Ｂａ０．６５Ｐｂ０．３５）ＴｉＯ３中分别掺入了Ａｌ２Ｏ３，ＳｉＯ２，Ｌａ２Ｏ３，ＭｎＯ２和ＴｉＯ２．讨论了每种掺杂物与烧成气氛和升温制度对常温电阻率的影响，找出了ＰＴＣ陶瓷的最佳组成；１ｍｏｌ（Ｂａ０．６５Ｐｂ０．３５）ＴｉＯ３，０．００２ｍｏｌＡｌ２Ｏ３，０．００４ｍｏｌＳｉＯ２，０．０１ｍｏｌＴｉＯ２，０．００３ｍｏｌＬａ２Ｏ３，０．０００２ｍｏｌＭｎＯ２．这种ＰＴＣ陶瓷的表面温度为２７０℃，常温电阻率为５～８×１０３Ω·ｃｍ，时任性为２４０ｖ／ｍｍ．     

铅系复合钙钛矿Pb（Fe_（1／2）Ta_（1／2））O_3铁电陶瓷的介电弛豫

用普通合成法制备了纯钙钛矿结构相的Ｐｂ（Ｆｅ＿（１／２）＝Ｔａ＿（１／２））Ｏ＿３（ＰＦＴ）陶瓷，并进行了９００℃退火热处理。对其介电性质测试结果表明，未热处理与热处理过的ＰＦＴ陶瓷在０．１～１００ｋＨｚ频率下均表现出介电弥散性转变。未热处理的ＰＦＴ陶瓷最大介电常数对应的温度（Ｔ＿０）不随测量频率变化；热处理过的ＰＦＴ陶瓷在此频率范围Ｔ＿０值表现出明显的频率依赖性（频率色散），即ΔＴ＿０＝５℃。由此可以认为ＰＦＴ是弛豫铁电体。ＸＲＤ结果表明，未热处理的ＰＦＴ陶瓷无超晶格衍射；而热处理过的ＰＦＴ陶瓷则有较弱的（１１１）超晶格衍射。利用有序－无序转变理论及超顺电结构模型对其结构与性质进行了探讨。     

铅系复合钙钛矿Pb（Fe1／2Ta1／2）O3铁电陶瓷的介电弛豫特性

用普通合成法制备了纯钙钛矿结构相的Ｐｂ（Ｆｅ１／２Ｔａ１／２）Ｏ３（ＰＦＴ）陶瓷，并进行了９００℃退火热处理。对其介电性质测试结果表明，未热处理与热处理过的ＰＦＴ陶瓷在０．１￣１００ＫＨｚ频率下均表现出介电弥散性转变。未热处理的ＰＦＴ陶瓷最大介电常数对应的温度（Ｔ０）不随测量频率变化；热处理过的ＰＦＴ陶瓷在此频率范围Ｔ０值表现出明显的频率依赖性（频率色散），即△Ｔ０＝５℃。由此可以认为ＰＦＴ是弛豫     

LaCrO_3－NiMn_2O_4复合陶瓷的结构分析

将尖晶石型ＮｉＭｎ＿２Ｏ＿４及钙钛矿型ＬａＣｒＣ＿３这二者电阻个较高的半导体陶瓷热敏材料复合并经高温烧结后，其复合体电阻率大幅度降低。应用ＸＲＤ，ＸＰＳ，ＴＥＭ和ＳＥＭ对复合体结构进行较为系统的研究，结果表明：ＮｉＭｎ＿２Ｏ＿４与ＬａＣｒＯ＿３按一定比例复合后，在烧结过程中两者之间有离子迁移发生，离子迁移的结果使钙钛矿结构的ＬａＣｒＯ＿３转变为高导电相的Ｌａ［Ｃｒ＿（１－ｘ－ｙ）Ｎｉ＿ｘＭＮ＿ｙ］Ｏ＿３（０＜ｙ＜０，０＜ｘ＋ｙ＜０），它使复合体电阻率大幅度降低。     

pH值对Ti（O~nBu）_4－Ba（OAc）_2水解法合成BaTiO_3粉体

以乙酸和氢氧化钾为辅助原料，通过Ｔｉ（Ｏ￣ｎＢｕ）＿４－Ｂａ（ＯＡｃ）＿２水解法合成ＢａＴｉＯ＿３粉体。借助ＳＥＭ、ＴＥＭ、ＸＲＤ和ＥＰＭＡ等分析手段，研究了ｐＨ值对ＢａＴｉＯ＿３粉体性能的影响。论述了合成ＢａＴｉＯ＿３的反应机理，同时探讨了ｐＨ值对其反应机理的影响。     

丙烯在SO_4~（2－）／M_xO_y固体超强酸催化剂上齐聚过程的研究

考察了丙烯在Ｍ＿ｘＯ＿ｙ固体超强酸催化剂上的齐聚过程。实验表明，催化剂的活性顺序为Ｚ＿ｒＯ＿２＞ＴｉＯ＿２，而Ｆｅ＿２Ｏ＿３催化剂几乎无活性。ＦＴ－ＩＲ表明，ＺｒＯ＿２催化剂具有超强酸的３个特征吸收峰，即１０５０、１１３０和１２２０ｃｍ￣（－１）。ＸＲＤ分析表明，ＺｒＯ＿２为非结晶态，而未浸Ｈ＿２ＳＯ＿４的ＺｒＯ＿２没有上述３个特征吸收峰，且以晶态存在。在Ｔ＝１３０℃、Ｐ＝４．０ＭＰａ、ＬＨＳＶ＝１．０ｈ￣（－１）和丙烯浓度为５０％的条件下，１００ｈ的稳定性试验表明，丙烯平均转化率为６９．５％，壬烯选择性为４５．５％和十二烯选择性为４１．６％。     

Si_3N_4－ZrO_2陶瓷中ZrN的生成及其对性能的影响

研究了ＺｒＮ在Ｓｉ＿３Ｎ＿４－ＺｒＯ＿２复相陶瓷中的形成及其对材料性能的影响，结果表明：在１．５ＭＰａＮ２气压烧结条件下，ＺｒＮ的形成温度约为１６００℃，提高Ｎ＿２的压力有利于抑制ＺｒＮ的生成，以稳定的ｔ－ＺｒＯ＿２加Ｓｉ＿３Ｎ＿４基体中，对抑制ＺｒＮ的生成有明显作用。当复相陶瓷中生成一定量的ＺｒＮ时，力学性能明显下降，而ＺｒＯ＿２分布均匀且以ｔ－ＺｒＯ＿２，ｃ－ＺｒＯ＿２形式存在时，复相陶瓷具有较高的强度（７４０ＭＰａ）和断裂韧性（８．８ＭＰａ·ｍ￣（１／２））。     

BaTiO3系陶瓷电压非线性特性研究

对ＢａＴｉＯ３－ＢａＺｒＯ３,ＢａＴｉＯ３－ＢａＳｎＯ３,ＢａＴｉＯ３－ＳｒＴｉＯ３非线性陶瓷材料的介电性能（ε,ｔａｎδ）与外ＢａＺｒ０．１３Ｔｉ０．８７Ｏ３,ＢａＳｎ０．０６Ｔｉ０．９４Ｏ３在直流偏压下ε可变化１．５￣２．７倍;在交流电压下ε可变化２￣２．５倍,且具肮介电常数、较高抗电强度,可用作开关电源ＲＣＤ保护电路的非线性陶瓷电容器和荧光灯无触点起辉器材料,Ｂａ１－ｘＳｒｘＴｉＯ３在直流偏     

Atomic Resolution Transmission Electron Microscopy of the Microstructure of Ordered Ba(Cd1/3Ta2/3)O3 Perovskite Ceramics

Microstructures of ordered Ba(Cd_1/3Ta_2/3)O₃ perovskite dielectric ceramics with and without a boron additive have been observed by atomic resolution transmission electron microscopy (TEM). The selected area electron diffraction and lattice image show a well-ordered structure with hexagonal symmetry (lattice constants of a ∼5.8 Å and c ∼7.1 Å) in the ordered Ba(Cd_1/3Ta_2/3)O₃ with a boron additive, which is similar to those in ordered Ba(Zn_1/3Ta_2/3)O₃ and Ba(Mg_1/3Ta_2/3)O₃ ceramics. Ordered domains with a twin crystallographic relationship and high-density domain interfaces induced by ordering were observed in the ordered Ba(Cd_1/3Ta_2/3)O₃ without a boron additive sintered at a relatively high temperature. Atomic resolution TEM further revealed the conservative twin boundaries along (001) and (110) planes and non-conservative antiphase boundaries with a projected displacement vector of the type [001] in the ordered Ba(Cd_1/3Ta_2/3)O₃ without a boron additive. Finally, the energetics of different domain interfaces are discussed with the interfacial structures in ordered Ba(Cd_1/3Ta_2/3)O₃ ceramics revealed by an electron microscope.     

Piezoelectric properties of Pb(Mn1/3Nb2/3)O3–PbZrO3–PbTiO3 ceramics with sintering aid of 2CaO–Fe2O3 compound

Since the electromechanical devices move towards enhanced power density, high mechanical quality factor (Q_m) and electromechanical coupling factor (k_p) are commonly needed for the high powered piezoelectric transformer with Q_m≥2000 and k_p=0.60. Although Pb(Mn_1/3Nb_2/3)O₃–PbZrO₃–PbTiO₃ (PMnN–PZ–PT) ceramic system has potential for piezoelectric transformer application, further improvements of Q_m and k_p are needed. Addition of 2CaO–Fe₂O₃ has been proved to have many beneficial effects on Pb(Zr,Ti)O₃ ceramics. Therefore, 2CaO–Fe₂O₃ is used as additive in order to improve the piezoelectric properties in this study. The piezoelectric properties, density and microstructures of 0.07Pb(Mn_1/3Nb_2/3)O₃–0.468PbZrO₃–0.462PbTiO₃ (PMnN–PZ–PT) piezoelectric ceramics with 2CaO–Fe₂O₃ additive sintered at 1100 and 1250 °C have been studied. When sintering temperature is 1250 °C, Q_m has the maximum 2150 with 0.3 wt.% 2CaO–Fe₂O₃ addition. The k_p more than 0.6 is observed for samples sintered at 1100 °C. The addition of 2CaO–Fe₂O₃ can significantly enhance the densification of PMnN–PZ–PT ceramics when the sintering temperature is 1250 °C. The grain growth occurred with the amount of 2CaO–Fe₂O₃ at both sintering temperatures.     

Ce-Y(Ca)-TZP陶瓷及Ce-TZP/Al2O3复相陶瓷的研究与应用进展

氧化铈稳定的四方氧化锆多晶陶瓷(Ce-TZP)具有良好的抗低温老化性和很高的断裂韧性(K_IC>20 MPa·m^1/2),但是弯曲强度较低(500 MPa左右)。如何在保留Ce-TZP陶瓷的抗低温老化性和高断裂韧性的同时,提高其强度,是本领域研究人员共同关心的问题。大量研究表明,通过添加其他固溶离子(如Y³⁺)达到共稳定效果和引入第二相(如Al₂O₃)获得细晶Ce-TZP基的复相陶瓷,可以显著提高材料的断裂强度,综合改善其力学性能。本文对CeO₂与其他氧化物共稳定的ZrO₂陶瓷及Ce-TZP/Al₂O₃复相陶瓷的研究进展进行了综述,并以义齿种植和增材制造为例介绍了其应用现状。     

Mn-Fe-Ce/TiO2低温NH3选择性催化还原NO

采用浸渍法制备了MnO2-Fe2O3-CeO2/TiO2催化剂用于低温NH3选择性催化还原烟气中NO,考察了Mn, Fe, Ce含量及焙烧温度对NH3选择性催化还原NO的活性和抗水性能的影响. 在气体体积空速(GHSV)=24000 h-1, NH3/NO=0.8(j), 350℃煅烧和烟气含3%(j) O2的条件下,该系列催化剂的脱硝活性为MnO2-Fe2O3-CeO2/TiO2>MnO2- Fe2O3/TiO2>MnO2/TiO2,且在200℃时MnO2(10)-Fe2O3(5)-CeO2(5)/TiO2的脱硝率为95%. 对含10%(j)水蒸汽的烟气,MnO2(10)-Fe2O3(5)-CeO2(5)/TiO2的脱硝活性维持在87%;在10%(j)水蒸汽和100′10-6 SO2共存条件下,短时间内脱硝活性维持在55%.     

Bi0.75Sr0.25MnO3的多铁性

采用溶胶-凝胶的方法制备了Bi0.75Sr0.25MnO3化合物,并对其结构、磁性质、铁电性进行了研究。X射线衍射结果显示样品为单相钙钛矿结构,电阻率和差热实验证实了样品在590K的温度附近发生了电荷有序相变。磁性质测量表明样品在低温下（5K）为铁磁性。电滞回线测量显示样品在室温下最大的剩余极化强度Pr为4．47×10...     

Large electric field induced strain of Bi(Mg1/2Ti1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics textured by Template Grain Growth

<001> oriented xBi(Mg_1/2Ti_1/2)O₃-(0.7-x)Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (BMT-PMN-PT) textured ceramics are successfully fabricated by the template grain growth method using BaTiO₃ platelets as template. BMT-PMN-PT textured ceramics with different BMT contents are studied in terms of crystal structure, microstructures, dielectric and ferroelectric properties, and electric field induced strain. The as-fabricated BMT-PMN-PT textured ceramics were found to have a strong orientation along <001> direction. The frequency dispersion of dielectric constant of BMT-PMN-PT textured ceramics increases gradually and its relaxability becomes stronger with increasing BMT content. A large electric-field induced strain (0.42 % at 4 kV/mm) is obtained in 0.25BMT-0.45PMN-0.3PT textured ceramics with Lotgering factor 0.94, which is about 83 % enhancement than that of the randomly oriented ceramics (0.23 % at 4 kV/mm). The strain of 0.25BMT-0.45PMN-0.3PT textured ceramics have a relatively high thermal stability, with a slight decrease from 0.42 % to 0.28 % in the temperature range of 20−100 °C. Our research suggests that 0.25BMT-0.45PMN-0.3PT textured ceramics have a greatly potential for actuator devices applications owing to its advantages of large electric field induced strain response.     

(1-x)Ba(Mg1/3Nb2/3)O3-xBaSnO3陶瓷的微波介电性能

用传统陶瓷制备方法制备了(1-x)Ba(Mg1/3Nb2/3)O3-xBaSnO3[0.0≤x≤0.3,(1-x)BMN-xBS]体系微波介质陶瓷,研究了该陶瓷的微观结构和微波介电性能.用X射线衍射仪研究陶瓷的晶体结构.用扫描电镜观察陶瓷的显微结构.用网络分析仪测试陶瓷的微波介电性能.结果表明:晶格常数c和a均随x值的增加而增加;晶格常数比(c/a)随x值的增加而减小.当x≥0.1时,1∶2有序衍射峰消失.陶瓷的平均晶粒尺寸在0.7～2 μm之间.随x值的增加,陶瓷的相对介电常数(εr)和谐振频率温度系数(τr)呈线性减小;品质因数与谐振频率的乘积(Qf)呈非线性变化.当x=0.15时,Qf达到最大值,为86 200 GHz.当x=0.3时,在此体系中可以获得τf接近零的微波介质陶瓷Ba(Sn0.3Mg0.233Nb0.467)O3,其微波介电性能如下:εr=26.1;Qf=42 500GHz;τr=4.3×10-6/℃.     

Fabrication of 0.24Pb(In1/2Nb1/2)O3-0.42Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 transparent ceramics by conventional sintering technique

0.24Pb(In_1/2Nb_1/2)O₃-0.42Pb(Mg_1/3Nb_2/3)O₃-0.34PbTiO₃ transparent ceramics were fabricated by a conventional sintering technique. Through optimization of sintering conditions of calcination and sintering temperatures and time, the obtained ceramics showed high optical transmittance of 53% and 71% at light wavelengths of 1300 and 2000 nm, respectively. The ceramics showed a rhombohedral to tetragonal phase transition at ~120°C and a tetragonal to cubic phase transition at 222°C. These transition temperatures were higher than those of 0.67Pb(Mg_1/3Nb_2/3)-0.33PbTiO₃ ceramics. In addition, the ceramics had a ferroelectric hysteresis loop, a large piezoelectric constant d₃₃ of 407 pC/N, and a planar electromechanical coupling factor k_p of 52%. These results suggest that the transparent ceramics may be used as a temperature-stable, linear electro-optic material.     

Sm掺杂Pb(Mg1/3Nb2/3)O3-PZT压电陶瓷的研究

本文通过一步反应合成法制备了铌镁-锆钛酸铅(Pb(Mg_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃,PMN-PZT)压电陶瓷,研究了稀土元素钐(Sm)掺杂对PMN-PZT(x%(摩尔分数)Sm-PMN-PZT)结构与电学性能的影响规律,得到了具有高压电性、高机电耦合系数和高居里温度的压电陶瓷。当x=2.0时,压电常数d₃₃=611 pC/N,机电耦合系数k_p=0.68,介电损耗tan δ=1.65%,相对介电常数ε_r=2 650,居里温度T_C=283 ℃。测试压电陶瓷电致应变性能,在3 kV/mm下单极电致应变达到0.20%,显示出其大应变材料的特征。结果表明,Sm掺杂PMN-PZT压电陶瓷具有优异的综合电学性能,有望在换能器、传感器以及致动器等领域广泛应用。     

Ba1-3x/2Lax(Mg1/3Ta2/3)O3陶瓷的微波介电性能

采用固相合成法制备了Ba1-3x/2Lax(Mg1/3Ta2/3陶瓷,研究了La掺杂对钽镁酸钡的结构和微波介电性能的影响.结果表明:A位取代能改进其烧结性能.在x≤0.02时,烧结样品为单相的钙钛矿结构,B位离子1:2有序;当x>0.02时出现第二相Ba0.5TaO3.B位离子有序度随着x的增大先增加后减小,在x=0.04时出现最大值.x≤0.02时介电常数变化较小,而后其值逐渐增大.品质因数与谐振频率的乘积(Q×f)值随着x的增大先增大后减小,在x=0.02时取得最大值;谐振频率温度系数(τf)值随着x增大而增大.