Adhesive-Bonded Ca(Mg_(1/3)Nb_(2/3))O_3/Ba(Zn_(1/3)Nb_(2/3))O_3 Layered Dielectric Resonators

Ca(Mg_ 1/3 Nb_ 2/3 )O_3 and Ba(Zn_ 1/3 Nb_ 2/3 )O_3 ceramic cylinders with the same diameter were bonded by adhesive with low dielectric loss to yield the layered dielectric resonators, and the microwave dielectric characteristics were evaluated with TE_ 01δ mode. With increasing the Ba(Zn_ 1/3 Nb_ 2/3 )O_3 thickness fraction, the resonant frequency (f_0) decreased, while the effective dielectric constant (ε_ r,eff ) and temperature coefficient of resonant frequency (τ_f) increased. Good microwave dielectri...     

Pb（Cd_（1／2）Te_（1／2））O_3及三元系压电陶瓷Pb（Cd_（1／

研制了一种新的三元系统压电陶瓷材料Ｐｂ（Ｃｄ１／２Ｔｅ１／２）Ｏ３－ＰｂＺｒＯ３－ＰｂＴｉＯ３，本系统材料压电性强，时间稳定性极佳，其时间稳定性比改性的ＰＣＭ提高一个数量级，作者认为稳定性的提高原因，不是由于材料的“软化”，而在于Ｔｅ６＋离子在电畴界面的偏聚对畴壁的“钉扎”作用，确定了Ｐｂ（Ｃｄ１／２Ｔｅ１／２）Ｏ３是顺电相其含量以４～６ｍｏｌ％为宜，部分Ｃｄ２－取代，使本系统材料“硬化”．     

Relaxor behavior of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics

n the present work, the phase transitions and relaxor behavior of (1−x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-PT, x = 0.2―0.4) ferroelectric ceramics have been investigated by means of X-ray diffraction, di-electric spectroscopy, the P-E hysteresis loop measurements and Raman scattering techniques. Structural analysis revealed that with the increase of PbTiO₃ content, PMN-PT ceramics experienced a gradual phase transition process from rhombohedral to tetragonal. It is usually believed that such kinds of phase transitions resulted in the linear decrease of relaxation degree. Surprisingly, our analy-sis of the dielectric spectra revealed that the indicator of the degree of diffuseness γ reached the maximum value near morphotropic phase boundary (MPB) (x = 0.32), then decreased with the further increase of PbTiO₃ content. The large dielectric relaxor feature near MPB may be attributed to the for-mation of ordered nanodomains, resulting from complex coexisting nanostructures. Further, the P-E hysteresis loop measurements and Raman analysis of the B-site cation order correlated well with the dielectric measurement results. It was found that the hysteresis loop squareness R_sq received the minimum value while the inverse of the value of full wide of half maximum (FWHM) of A_1g mode reached the maximum value at MPB composition, which showed similar trends to γ.     

0.74Pb(Mg_(1/3)Nb_(2/3))O_3-0.26PbTiO_3薄膜的光学性能研究

采用磁控溅射法,选用LaNiO3(LNO)作为缓冲层和电极层,在硅基片上成功地制备出了0.74Pb(Mg1/3Nb2/3)O3-0.26PbTiO3(PMN-0.26PT)铁电薄膜.X射线衍射(XRD)分析表明薄膜具有沿(110)方向择优取向的钙钛矿结构.利用NKD光谱测试仪测试了薄膜的反射谱,并使用最小二乘法进行拟合分析得到其折射率和消光系数.在沉积温度为500℃时,薄膜具有更为均匀和致密的微观结构.在波长为633 nm时,该薄膜的折射率大小为2.41.薄膜的折射率和消光系数随着光子能量的增加而增加.薄膜的这些光学特性使其有望在低压电光转换器、光波导等器件中应用.     

关于单K3-群L3(3)和U3(3)

设G为有限群,o1(G)表示G中最高阶元素的阶。用极少的数量刻画有限单群是单群刻画领域中一个有趣的课题。本文只用群的阶及最高阶元素的阶刻画了单K3-群L3(3)和U3(3),即证明了： 设G为有限群, M 为单K3-群L3(3)和U3(3),则GM当且仅当|G|=|M|,且o1(G)=o1(M)。
     

Optimizing the Synthetic Conditions of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 from a Carbonate Co-precipitation Method

1 Introduction As a promising cathode material for lithium ion batteries,LiNi1/3Co1/3Mn1/3O2 attracted intensive attentions.Owing to high specific capacity,long circle life and excellent safety,it may be an alternative candidate for LiCoO2.As a complex composite,however,it is difficult to synthesize phase-pure LiNi1/3Co1/3Mn1/3O2 by a simple mixed calcination method[1].From this concern,carbonate co-precipitation method,which can prepare homogeneous LiNi1/3Co1/3Mn1/3O2 with typical layered structure,bec...     

准同型相界附近0.02Pb(Zn_(1/3)Nb_(2/3))O_3-0.50Pb(Ni_(1/3)Nb_(2/3))O_3-0.48Pb(Zr_xTi_(1-x))O_3陶瓷压电性能研究

采用传统固相反应法制备四元系0.02Pb(Zn1/3Nb2/3)O3-0.50Pb(Ni1/3Nb2/3)O3-0.48Pb(ZrxTi1-x)O3(0.29≤x≤0.34)陶瓷.观察样品的晶相结构和显微结构,测试压电性能和介电性能.随着Zr/Ti比的增大,晶相从四方相向三方相转变.发现准同型相界位置在x=0.32附近.1 240℃烧结的0.02PZN-0.50PNN-0.48PZ32T陶瓷展现了良好的压电性能,压电常数d33为715 p C/N,机电耦合系数kp为0.541,剩余极化强度Pr为25.5μC/cm2,矫顽场强Ec为5.6 k V/cm.新的压电材料适合高性能压电器件应用,且简单的制备方法给生产带来极大便利.     

(Lal-xSmx)2/3Sr1/3MnO3材料的巨磁致伸缩及磁电阻效应

采用溶胶凝胶法制备了一系列的多晶(La1-xSmx)2/3Sr1/3MnO3样品,X射线衍射研究表明,随Sm含量的增加,样品出现从菱面相向正交相结构的转变,在低温下观察到一定Sm含量的样品具有约-180×10-6大小的磁致伸缩和320%的磁电阻效应,在室温下,样品的磁致伸缩和磁电阻随Sm含量的变化有类似的关系.     

BiFeO3掺杂Pb（In1/2Nb1/2）O3-Pb（Mg1/3Nb2/3）O3-PbTiO3陶瓷的制备与磁电性能研究

以固相合成法制备了铁酸铋（BiFeO₃,简称BFO）掺杂的铌铟酸铅-铌镁酸铅-钛酸铅（Pb（In_1/2Nb_1/2）O₃-Pb（Mg_1/3Nb_2/3）O₃-PbTiO₃,简称PIN-PMN-PT）多铁性陶瓷材料,X射线衍射（XRD）测试结果表明：样品具有钙钛矿结构,电滞回线显示其铁电性良好,剩余极化值（P_r）可达18 μC·cm^-2.由于BiFeO₃掺杂后,样品电矩减小,氧空位增多,使其铁电畴翻转困难,样品的电性能略有下降,但是其磁性能随BiFeO₃掺入量的增加而逐渐增强,且样品居里温度（T_m）为200℃左右.该材料在电磁学领域有望成为具有应用前景的多铁性材料.     

共沉淀法合成Ni_(1/3)Co_(1/3)Mn_(1/3)(OH)_2的热力学分析

对Me2+(Me=Ni,Co,Mn)-NH3-OH--H2O共沉淀反应体系进行了热力学分析,采用共沉淀法合成了LiNi1/3Co1/3Mn1/3O2正极材料前驱体Ni1/3Co1/3Mn1/3(OH)2,研究了pH值和氨水浓度[N]对前驱体振实密度的影响.热力学分析表明:以氢氧化钠为沉淀剂、氨水为络合剂,采用共沉淀法合成前驱体的最佳pH值为11,最佳[N]为0.1～0.5mol/L;在此条件下,金属阳离子Ni2+、Co2+和Mn2+的损失最小,分别小于1×10-3、1×10-3和1×10-6mol/L.在pH=11、[N]=0.24mol/L条件下,所合成的前驱体中Ni、Co、Mn的摩尔比为0.324∶0.349∶0.327,与理论设计值1∶1∶1非常接近,其振实密度高达1.32g/cm3.     

Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 Complex Perovskite Ferroelectric Ceramics with High Dielectric Constant and Low Firing Temperature

The effects of different firing temperatures on the stability of perovskite phase, grain size, and dielectric properties were investigated by XRD, TEM, SEM and dielectric measurements. The dielectric ceramics of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃-BaTiO₃ system were obtained by chemical coprecipitation in water. The ceramics have higher dielectric constant (7003-9714), lower firing temperature(950-1150℃), quite uniform microstructure with grain size less than 2.5 mp, and lower temperature coefficients of capacitance. As a result, it was confirmed that the simple and low cost chemical route used namely coprecipitation in water is a desired method for preparing high property dielectric materials applicable to multilayer capacitors.     

弛豫铁电单晶铌镁酸铅-钛酸铅的工程畴结构研究

综述了目前对铁电晶体畴结构进行观测的主要技术方法,及国内外相关研究单位对新型弛豫铁电单晶铌镁酸铅-钛酸铅[(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-xPT)]的工程畴结构的研究进展。以往的研究表明,该类单晶的机电性能与其工程畴结构之间存在着密不可分的关系,这些研究结果对阐明PMN-xPT单晶在不同极化方向与工程畴结构状态下,其优异机电性能的起源机制与发生规律,进而指导剪切波换能器、垂直极化方向的大应变驱动器等电机器件的设计与制作,具有重要的理论意义与实际应用价值。     

Na3La2(BO3)3∶Tm3+的合成及其光谱特性

论文用固相反应法,合成了一系列掺Tm     

茂金属/烷基铝/B(C6F5)3催化体系催化乙烯聚合

Cp2ZrCl2、Et(Ind)：ZrCl2与烷基铝原位生成二烷基化茂金属．然后与B(C6F5)3作用组成新的催化体系，研究了这种催化体系对乙烯聚合的影响、发现用三乙基铝的体系对乙烯聚合没有活性，用三异丁基铝的体系对乙烯聚合有较高活性，其原因在于形成了不同的活性中心，用紫外光谱的方法研究活性中心的结构及其变化，并与聚合活性进行了关联。     

(La0.9Dy0.1)2/3Ba1/3Mn1-xAlxO3(x=0,0.05)氧化物的结构与磁性

【目的】为改善(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3的磁热性能,研究掺杂Al对其晶体结构、居里温度、相变类型以及磁热性能的影响。【方法】采用固相反应法制备锰氧化物(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3(x=0,0.05)样品,利用X射线衍射法分析样品的结构,用振动样品磁强计测量样品的磁性。【结果】所制备样品均为单相钙钛矿结构,属于菱方晶系,空间群为R-3c(No.167)。掺杂Al使样品居里温度由无掺杂的274K降低到248K,在外加磁场变化为20kOe时最大磁熵变由2.16J/(kg·K)降低到1.85J/(kg·K)。样品的铁磁-顺磁相变属于二级相变。采用双交换作用机制解释了居里温度和磁化强度的变化。【结论】非磁性元素Al替代Mn不改变其晶体结构,稍微降低了锰氧化物的磁热性能。     

Magnetic properties of Fe3(1−x)Cr3xC alloys

The magnetic properties of Fe_3(1−x)Cr_3xC alloys with x=0.05, 0.1, 0.15, and 0.2, which crystallize in the cementite Fe₃C-type structure with space group Pnma, were investigated by means of magnetization measurements. These alloys show temperature-induced second-order magnetic phase transitions. The Curie temperature (T_c) of these alloys decreases with increasing x. The isothermal magnetic-entropy changes of these alloys were derived from the magnetic isotherms measured with increasing temperature and increasing field. The maximum values of the magnetic-entropy change are about 0.9 and 3.6 J·kg⁻¹·K⁻¹ at T_c =360 K for x = 0.05 in a magnetic field change from 0 to 1 T and 0 to 5 T, respectively.     

关于Diophantine方程Sx(n)=Sy(3)

摘要设Sm(n)是第m个n角数，给出当n-2为平方数时方程Sx(n)=Sy(3)的全部解的通式，并证明当n-2为非平方数时该方程有无穷多组正整数解．     

关于方程Sx（n）=Sy（3）的商榷

与第m个n角数Sm(n)相联系的方程Sx(n)=Sy(3),证明了：（1）当D＝n-2是非平方数,且u12-Dv12=-1有解（u1,v1)时,则该方程有无穷多组解。（2）当n-2是非平方数时,该方程或者无解或者有无穷多解,举例说明了结论（1）中u12-Dv12=-1有解的条件不是必要的,还指出文献[3]中的错误。