LaCrO3—NiMn2O4复合陶瓷的结构分析

将尖晶石型ＮｉＭｎ２Ｏ４及钙钛矿型ＬａＣｒＯ３这二者电阻率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：ＮｉＭｎ２Ｏ４与ＬａＣｒＯ３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ＬａＣｒＯ３转变为高导电相的Ｌａ［Ｃｒ１－ｘ－ｙＮｉｘＭｎｙ］Ｏ３（０〈ｘ〈１，０〈ｙ     

钡锶铅氧化物陶瓷的结构与热敏性

本文应用共沉淀法制备了Ｂａ１－ｘＳｒｘＰＢ１＋ｙＯ３－δ（Ｘ＝０，０．１，０．３．０．５，０．７，１；ｙ＝０．０．１．０．２，０．３）陶瓷试样。测定了试样的电阻－温度特性。并对样品进行了Ｘ射线衍射分析（ＸＲＤ）和扫描电子显微镜（ＳＥＭ）的观察，以研究Ｓｒ掺杂ＢａＰｂＯ３陶瓷的结构和热敏性。实验结果表明：掺杂钡铅氧化物陶瓷仍是钙钛矿结构。随着Ｘ含量增加（ｙ为定值）陶瓷的ＰＴＣＲ温度升高，但ＰＴＣＲ效应逐渐降低；ｙ＝０时，几乎没有ＰＴＣＲ效应．ｙ＞０．２时，ＰＴＣＲ效应也不明显，而在０＜ｙ≤０．２时，ＰＴＣＲ效应随ｙ值的增加而增大。     

常压下的Ca(Mn_(3-x)Cu_x)Mn_4O_(12)样品的制备及其导电机制的研究

钙钛矿结构ＣａＣｕ３Ｍｎ４Ｏ１２的传统制备方法是热压法（几万个大气压,１０００℃）。人们发现它的居里点Ｔｃ＝３５５ Ｋ,磁电阻ＭＲ值比相同条件下的Ｌａ０．６Ｙ０．０７Ｃａ０．３３ＭｎＯａ大得多,并且从低温到高于居里点的温度范围内都存在较大的磁电阻值。另外,Ｃａ（Ｍｎ３－ｘ Ｃｕｘ） Ｍｎ４Ｏ１２（ｘ＝３）的饱和磁化场,在室温３００Ｋ时,饱和磁化场仅为０．０３Ｔ。本实验中,在常压和１０７０ Ｋ的条件下合成了Ｃａ（Ｍｎ３－ｘＣｕｘ）Ｍｎ４Ｏ１２,从而大大简化了Ｃａ （Ｍｎ３－ｘＣｕｘ）Ｍｎ４Ｏ１２的制备条件。关于该材料的导电机制,铁磁磁畴再取向饱和场与磁电阻饱和场相同,表明Ｃａ（Ｍｎ３－ｘ Ｃｕｘ）Ｍｎ４Ｏ１２的ＭＲ来源于磁畴间或颗粒间的隧道机制。     

新的稀土锂钒酸盐的合成,结构和发光

本文首次报道了在６００℃灼烧数小时合成出新的稀土锂钒醛盐Ｙ０．５－ｘＬｉ１．５ＶＯ４；ＲＥｘ（ＲＥ＝Ｓｍ＾３＋，Ｄｙ＾３＋，Ｈｏ＾３＋，Ｅｒ＾３＋，Ｔｍ＾３＋）（０．０１＜ｘ＜０．０１）多晶粉末。比通常钒酸盐的合成温度降低近４００℃。用Ｘ射线粉末法分析此多晶粉末的结构。     

四元系统PbO－BaO－SrO－Nb_2O_5介电性能研究

对四元系统ＰｂＯ－ＢａＯ－ＳｒＯ－Ｎｂ＿２Ｏ＿５的介电性能进行了研究。Ｘ射线粉末衍射图谱确证在ＰｂＯ，ＢａＯ，ＳｒＯ，Ｎｂ＿２Ｏ＿５一定配比下，该系统为四方钨青铜铁电陶瓷系统，其主晶相为Ｐｂ＿ｘＢａ＿ｙＳｒ＿ｚＮｂ＿（１０）Ｏ＿（３０）（１．７５≤ｘ≤２，１．２５≤ｙ≤２，１≤ｚ≤１．７５）。在此基础上，通过加入各种添加剂合理的掺杂改性，成功地研制出一种新型中温烧结高ε的Ｘ７Ｒ瓷料，此料适合作ＭＬＣ。这一研究在国内至今为止未见报道，在国外亦属少见。     

SrFe1.5-xCoxOy混合导体的制备及氧化扩散研究

详细研究了混合离子导体ＳｒＦｅ１．５－ｘＣｏｘＯｙ（ｘ＝０．０－０．５）的相组成和氧化学扩散性质。Ｘ射线衍射和扫描电镜分析表明：该体系随Ｃｏ含量的增加由Ｓｒ４Ｆｅ６－ｘＣｏｘＯ１３＋δ层着相逐步变为含钙钛矿等物相的多相区。     

流态化CVD技术制备Al_2O_3－SnO_2复合粒子

在内径４０ｍｍ的流化床反应器中，利用ＳｎＣｌ＿４气相水解反应，制备了超细Ａｌ＿２Ｏ＿３－ＳｎＯ＿２复合粒子。通过ＸＲＤ，ＥＰ－ＭＡ，ＨＲＥＭ等现代化分析手段确定了产物中ＳｎＯ＿２的晶型及其在Ａｌ＿２Ｏ＿３团聚物中和在Ａｌ＿２Ｏ＿３原生颗粒表面的分散包敷形态。研究结果表明：３００℃下制备的产物中ＳｎＯ＿２呈无定态，经８００℃热处理２ｈ，ＳｎＯ＿２转化成金红石型，产物中ＳｎＯ＿２均匀分散于整个Ａｌ＿２Ｏ＿３团聚物中；１００℃下制备的产物中ＳｎＯ＿２以薄膜形式包敷在超细Ａｌ＿２Ｏ＿３颗粒表面；４５０℃下制备的产物中，ＳｎＯ＿２以６～１０ｎｍ的粒子形式淀积在Ａｌ＿２Ｏ＿３表面。     

焦磷酸锶镁：锡荧光体的发光特性

本文用高温固相反庆法合成了（Ｓｒ１－ ｘ Ｍｘ ）２Ｐ２Ｏ７ ∶Ｓｎ （３．３×１０－ ２）和（Ｓｒ０．９Ｍｇ０．１）２Ｐ２Ｏ７∶ｘＳｎ 两个体系系列样品,在紫外线激发下,详细测定了它们的激发和发射光谱,讲座了Ｍｇ 含量对（Ｓｒ１－ ｘＭｇｘ）２Ｐ２Ｏ７∶Ｓｎ 和Ｓｎ 含量对（Ｓｒ０．９Ｍｇ０．１）２Ｐ２Ｏ７∶ｘＳｎ 体系发光性能的影响。     

复合电子陶瓷及其复合机制研究

通过大量实验研究，提出了一种多相陶瓷的复合机制。钙钛矿型（ＡＢＯ３）与尖晶石型（ＡＢ２Ｏ４）材料以一定比例进行复合，在高温烧结过程中有离子迁移发生，离子迁移主要在Ｂ位间进行。复合体的电导率与离子迁移后所形成的结构状态有关，当复合体中产生高电导结构时，复合体电阻率降低；反之，电阻率增高。     

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。     

LaMn1-xTixO3-NiMn2O4(0≤x≤0.7): A composite NTC ceramic with controllable electrical property and high stability

A series of NTC thermistor ceramics based on LaMn_1-xTi_xO₃-NiMn₂O₄(0≤x≤0.7) composite system have been fabricated by solid-state method. X-ray diffraction analysis indicates the composite ceramics mainly consisting of a rhombohedral perovskite LaMn_1-xTi_xO₃ phase and a cubic spinel NiMn₂O₄ phase. SEM images show high density of the as-prepared composite ceramics. The effects of the Ti doping and the weight ratio of LaMn_1-xTi_xO₃/NiMn₂O₄ on electrical property have been studied. The electrical resistivity ρ increases significantly with Ti addition increasing and decreases obviously with LaMn_1-xTi_xO₃ concentration increasing. The ρ_25°C and B values are in the range of 3.2–53,200.0Ω·cm and 1300–4008 K, respectively, and could be adjusted to desired values and applied in various fields. The conductive mechanism may be related to the ion migration and the percolation theory. After annealing at 125°C for 1000h, the resistance shifts are less than 0.52%, suggesting good stability of the composite and high potential for NTC thermistor applications.     

Mg掺杂对稀土钙钛矿型LaCrO3催化剂的结构和甲烷催化燃烧性能的影响

以柠檬酸为络合剂采用溶胶-凝胶法制备了纯LaCrO₃和Mg掺杂型催化剂，以X射线衍射法分析各样品的物相，BET法测定样品的比表面积，TPR技术表征样品的还原性能，以甲烷燃烧为探针反应考察各样品的催化氧化活性。实验结果表明，未掺杂Mg的样品为单一相钙钛矿LaCrO₃结构。Mg的掺杂即可破坏单相钙钛矿LaCrO₃结构的形成，明显削弱其衍射峰强度，同时产生LaCrO₄和La₂CrO₆及MgO物相，但提高了催化剂的还原能力，改善了催化活性。当加入Mg的质量分数为10%时催化活性最好。     

Highly dense 0.3CaCeNbWO8-0.7LaMnO3 composite ceramics fabricated by cold sintering process

The cold sintering process (CSP) has been used for fabricating functional ceramics at a low sintering temperature. In this study, highly dense 0.3CaCeNbWO₈-0.7LaMnO₃ composite ceramics have been successfully fabricated by CSP. The phase structure, microstructure, and electrical properties of composite ceramics have been investigated. The composite ceramic is mainly composed of a tetragonal CaCeNbWO₈ phase with scheelite structure and an orthorhombic LaMnO₃ phase with perovskite structure. The relative density of composite ceramic is 94.5%, and is higher than that of single phase ceramic. The resistivity of composite ceramic exhibits negative temperature coefficient characteristics, with an aging coefficient less than 2%. Such a sintering methodology is of great significance, since it provides a feasible idea for preparing composite ceramics.     

Pb（Zn1／3Nb2／3）O3基陶瓷固相反应中的相变过程

用两次合成工艺,按Pb(Zn_(1/3)Nb_(2/3))O_3(PZN)的化学计量比合成的陶瓷为一种立方焦绿石相和PbO的混合物,其中立方焦绿石相为主晶相。该焦绿石结构的分子式为Pb_2ZnNb_2O_8,Fd3m空间群,Z=6,α=10.62(?)。在PZN基陶瓷中引入钙钛矿结构的子晶(如BaTiO_3),将促进其周围的Pb_2ZnNb_2O_8与PbO结合,形成钙钛矿结构的Pb(Zn_(1/3)Nb_(2/3))O_3。     

铌锌酸铅基陶瓷相变的热力学分析

ＰＺＮ基陶瓷在烧结过程中都要经历由焦绿石相朝钙钛矿相的转变。ＰＺＮ基陶瓷中钙钛矿相含量的多少与添加剂的种类及数量密切相关，本工作根据化学热力学理论，讨论了内应力对化学势的影响，建立了一个热力学模型，并用该模型讨论了ＰＺＮ基陶瓷在烧结时的相变过程。     

0.74NaNbO3–0.26Sr(Mg1/3Nb2/3)O3 lead-free dielectric ceramics with high energy storage properties

Sodium niobate (NaNbO₃) ceramics are commonly investigated for use as energy storage ceramics because of their excellent properties. NaNbO₃ ceramics are modified mainly by doping with a Bi-based composite perovskite, that is, by the nonequivalent doping of Bi³⁺ at the A site of the NaNbO₃ ceramic. In addition, the high volatility of Bi at high temperatures increases the defects in the ceramics. This paper provides a new idea of doping modification of sodium NaNbO₃-based energy storage ceramics. Here, (1?x)NaNbO₃–xSr(Mg_1/3Nb_2/3)O₃ (x = 0.17, 0.20, 0.23, 0.26) ceramics were prepared by doping NaNbO₃ with an Sr-based composite perovskite. Compared with Bi-based composite perovskite, Sr-based composite perovskite doping of NaNbO₃ ceramics can also obtained good energy storage properties: a total energy storage density of 4.28 J/cm³ and an energy storage efficiency of 89.3%. In addition, the ceramics exhibited good frequency stability (2–200 Hz) and a high charge/discharge rate (1.06 μs).     

YSZ/MgAl_2O_4复合粉末的合成及其材料的烧成活化能

采用共沉淀法在1100℃制备了70%(体积分数,下同)氧化钇稳定氧化锆[xY2O3+(1-x)ZrO2,x=0.02,0.03,0.04,in mole,yttria stabilized zirconia,YSZ]-30%镁铝尖晶石(MgAl2O4)复合粉体,2种原始粉料的配料各为70%和30%,并在1200～1500℃常压烧成制备了陶瓷材料。结果表明:在制得的所有粉末中,未发现单斜相ZrO2;2YSZ(0.02Y2O3+0.98ZrO2,摩尔分数,下同)/MgAl2O4和3YSZ/MgAl2O4这2种粉体中的ZrO2为四方相多晶氧化锆;而4YSZ/MgAl2O4粉末中的ZrO2相为全稳定立方氧化锆。对于1500℃烧结制备的陶瓷材料,2YSZ/MgAl2O4块体中的ZrO2相为部分稳定氧化锆;而3YSZ/MgAl2O4和4YSZ/MgAl2O4块体中的ZrO2相为全稳定氧化锆。(2～4)YSZ/MgAl2O4复相陶瓷的活化能为(623±80)kJ/mol。     

Elimination of pyrochlore phase in high-concentration Sm3+-doped PMN-PT piezoelectric ceramics by excessive MgO

Undesirable pyrochlore phase often appears in Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT)-based ceramics with high rare-earth ion (RE³⁺) doping concentration, which greatly limits their development. In this study, 0–5 mol% Sm³⁺-doped Pb(Mg_1/3Nb_2/3)O₃-29PbTiO₃ (PMN-29PT:0-5Sm) ceramics were first synthesized using traditional precursor method. In the X-ray diffraction spectra and scanning electron microscope images of PMN-29PT:3-5Sm ceramics, the diffraction peaks of pyrochlore phase and pyrochlore grains with octahedral morphology were observed, respectively. The reason for the appearance of the pyrochlore phase is that Sm³⁺ doping causes the Nb-rich regions. To eliminate the pyrochlore phase, PMN-29PT:3-5Sm ceramics were resynthesized by an improved precursor method in which an excess of 4 mol% MgO was added to the reactants before pre-sintering. After adding an excess of 4 mol% MgO, the concentration ratio of Nb⁵⁺ and Mg²⁺ in the pyrochlore grains returned to the value in the perovskite grains, and the pyrochlore phase was transformed into the perovskite phase PMN. The dielectric, ferroelectric, and electromechanical properties were compared before and after eliminating the pyrochlore phase. The results show that the comprehensive performance of the ceramics is improved after eliminating the pyrochlore phase.     

烧结工艺对Si_3N_4/TiC纳米复合陶瓷材料微观结构及力学性能的影响

以La2O3和Y2O3作为复合烧结助剂,采用热压烧结法制备了Si3N4基复合陶瓷材料。研究了保温时间和烧结助剂含量对复合材料微观结构及力学性能的影响。研究表明:所制备的Si3N4/TiC陶瓷复合材料的微观结构呈现纵横交错、相互嵌套的结构,晶粒尺寸呈现明显的双峰分布特征,单位面积内晶粒数量与烧结助剂含量之间呈线性降低关系。当烧结助剂质量含量为8%时,该复合陶瓷材料具有最优的力学性能,其抗弯强度、断裂韧性和Vickers硬度分别达到943MPa,8.38MPa·m1/2和16.67GPa。