磁电复合材料CuFe2O4/PbZr0.53Ti0.47O3的内耗与介电损耗

制备了组分为xCuFe2O4-(1-x)PbZr0.53Ti0.47O3(其中x=0．1，0．2，0．3，1．0)的磁电复合材料，XRD实验表明，样品中只存在着CuFe2O4和PbZr0.53Ti0.4703相．利用多功能摆测量了样品在低频下(0.1--6．4Hz)的内耗，同时利用HP4194A阻抗分析仪测量了样品低频(100Hz--1 MHz)的介电损耗，分析了复合物中CuFe2o4和PZT对内耗及介电损耗分别所作的贡献．     

弛豫铁电体Pb(Mg1/3Nb2/3)O3-PbTiO3的相变

测量了(1-x％)镁铌酸铅-x％钛酸铅(1≤X≤11)(简称PMNTx)陶瓷样品的介电常数、内耗和Young’s模量．观测到在Tm温度附近，即在介电常数达到最大值时，出现一个内耗峰，并且模量发生软化．这反映了极化纳米微畴的弛豫．对于PMNTx(5≤x≤11)的样品，在Tm温度以下的某个温度出现附加的内耗峰和Young’s模量的异常，表明样品中发生了自发的弛豫铁电到铁电(简称R-F)的相变，对R-F相变的机制进行了讨论．     

湿度对Ba(Mg1/3Ta2/3)O3陶瓷介电性能的影响

深入研究了不同湿度条件下Ba(Mg1/3Ta2/3)O3(BMT)陶瓷的介电性能.采用模式识别和人工神经网络优化BMT陶瓷制备工艺参数,并对湿度稳定性进行了预报.结果表明,随湿度由12.4%RH升高到97.2%RH,1200℃烧结的BMT陶瓷的介电常数(ε)和介电损耗(tanδ)出现较大幅度提高,阻抗显著下降;与之相比,1400℃C烧结的BMT陶瓷尤其在高频条件下,介电性质随湿度变化不大.研究证明气孔率是影响BMT陶瓷介电性能对环境湿度稳定性的重要因素.     

FeCoV/Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3/Ni薄膜复合结构的磁电效应

为了适应器件的小型化、提高薄膜两相复合磁电材料的磁电效应,采用磁控溅射方法在Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT)衬底上生长FeCoV薄膜和Ni薄膜,形成FeCoV/PMN-PT/Ni薄膜复合结构。采用动态磁电系数测量系统对复合结构的磁电性能和共振频率进行了研究。结果表明:复合结构的磁电系数随直流偏置场的增加呈现先增加后减小的趋势,在约39.8kA/m附近达到峰值17.8×10-3 mV·cm-1·A·m-1,在31.84kA/m的直流偏置场下,磁电电压随着交流激励场强度的增加呈线性增加。复合结构在85.5kHz下具有一个明显的共振峰,在共振频率下,磁电性能提高5倍以上。     

Pb[(Mg1/3Nb2/3)0.536(Ni1/3Nb2/3)0.128Ti0.336]O3陶瓷的结构和电学性能

通过铌铁矿预产物法制备出了Pb[(Mgq/3Nb2/3)0.536(Ni1/3Nb2/3)0.128Ti0.336]O3铁电陶瓷,并对其结构和电学性能进行了研究.结果表明,该三元体系组成处在准同型相界区域,1kHz时的介电常数极值达到45540,剩余极化强度为37uC/gm2,压电系数d33也达到780pC/N.烧结时有效地抑制PbO的挥发对于获得高性能的铅系铁电陶瓷有决定性的影响.     

Polarization fatigue in Pb(In0.5Nb0.5)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals

Electric fatigue tests have been conducted on pure and manganese-modified Pb(In_0.5Nb_0.5)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PMN–PT) single crystals along different crystallographic directions. Polarization degradation was observed to suddenly occur above 50–100 bipolar cycles in 〈1 1 0〉 oriented samples, while 〈0 0 1〉 oriented samples exhibited almost fatigue free characteristics. The fatigue behavior was investigated as a function of orientation, magnitude of the electric field and manganese dopant. It was found that 〈0 0 1〉 oriented PIN–PMN–PT crystals were fatigue free, due to its small domain size, being on the order of 1 μm. The 〈1 1 0〉 direction exhibited a strong electrical fatigue behavior due to mechanical degradation. Micro/macro cracks developed in fatigued 〈1 1 0〉 oriented single crystals. Fatigue and cracks were the result of strong anisotropic piezoelectric stress and non-180° domain switching, which completely locked the non-180° domains. Furthermore, manganese-modified PIN–PMN–PT crystals were found to show improved fatigue behavior due to an enhanced coercive field.     

Indentation-induced domain switching in Pb(Mg1/3Nb2/3)O3–PbTiO3 crystal

Response of ferroelectric domains to mechanical stresses was studied on a <010> oriented piezoelectric 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (0.65PMN–0.35PT) crystal. Stress-induced domain switching was observed in the stress field of a microindentation and was confined to butterfly-shaped switching zones which extended preferentially along the <101> directions. Based on a critical shear stress criterion, a stress analysis was made to determine the condition for the 90° domain switching. The analysis predicted a hyperbolic contour for the switching-zone boundary, in agreement with the experimental observations.     

Additional transition induced by magnetoelectric interaction in ferroelectromagnet Pb（Fe1/2Nb1/2）O3

Besides the two phase transitions known in ferroelectromagnets, an additional transition was observed experimentally in Pb（Fe1/2Nb1/2）O3 and the possible mechanism was explored. The magnetic moment shows that anomalous increases when the temperature goes down away from the Neel temperature of 20-30 K. The existence of the hysteresis verifies the weak ferromagnetic property. This additional phase transition is considered to originate from the magnetoelectric coupling between the ferroelectric and antiferromagnetic orders in this compound. From the Moessbauer parameter analysis, it is confirmed that the hybridization of the O 2p, Fe 3d and Nb 4d electron states makes the realization of magnetoelectric coupling possible.     

(Ba1-xSrx)(Zn1/3Nb2/3)O3固溶体系统的晶体结构

XRD分析表明,(Ba1-xSrx)(Zn1/3Nb2/3)O3系统中生成了一定的第二相,第二相的形成与ZnO的挥发有关.随着Sr含量的增加,晶体结构由无序的立方相向有序的赝立方相转变.在低角度处出现了1:2超晶格衍射峰,在高角度处衍射峰展宽并右向偏移.(Ba1-xSrx)(Zn1/3Nb2/3)O3系统中氧八面体的畸变是相转变形成、有序相产生、晶体结构对称性下降及晶格常数a和c减小的根本原因.     

碱熔Nb2O5湿化学法合成Pb（Mg1／3Nb2／3）O3纳米粉体

以Nb2O5作为反应的起始物，采用一种新型湿化学方法制备复合钙钛矿型Pb（Mg1／3Nb2／3）O3（简称PMN）纳米粉体。利用激光拉曼光谱、DSC／TG、TEM和XRD对制备的Nb-柠檬酸铵络合溶液、干凝胶粉末和PMN粉体进行了表征。研究了焙烧工艺对PMN粉体的物相组成、晶粒尺寸及相含量的影响。实验结果表明：在适宜的焙烧条件下，PMN粉体的平均粒径小于50nm，PMN相的含量大于70％。适当升高焙烧温度及延长保温时间或者采取二次焙烧均能提高钙钛矿相PMN的含量，其中采用二次焙烧的方法效果显著。     

INTERNAL FRICTION AND ELASTIC CONSTANTS OF Pd-B-H ALLOYS

1.IntroductionInthePd(Hsystemthereexisttwophases:ana-phaseofl0whydrogenconcentrationandahigherconcentratedfi-phase.Ananalysisofactivitymeasurementswithintheframe-workofthequasi-chemicalappr0achsuggeststheexistenceofanattractiveinteractionofhydrogeninterstitialsviaelasticdeformation0fthePdlattice[1].Them0delpredictsthatatemperaturedependentfracti0n0fthehydrogenat0msisc1usteredintopairsorhigheror-derclustersinexcessoftherandomnumber0fpairs.Theapplicati0nofthistheoryt0theanal0gGusbinaryall0yPd-…     

La2Mo2O9系新型氧离子导体中氧空位扩散的内耗与介电弛豫研究

报道了用内耗和介电弛豫方法研究新型氧离子导体La2-xAxMo2O9(其中，A=Ca，Bi，K；x=0-0.3)的最新结果，结果表明，在内耗-温度谱和介电损耗-温度谱上出现了两个与氧空位短程扩散有关的内耗峰和介电弛豫峰，说明氧空位扩散至少有两个不等同的弛豫过程．掺杂后，两弛豫峰都移向高温，氧空位的扩散激活能增加，高温弛豫峰高度降低而低温弛豫峰略有升高．在适当的掺杂条件下(30％Ca，5％Bi或5％K)，低温下的电导率都有不同程度的提高．根据实验结果和晶体结构提出了氧空位(或离子)扩散的物理图像．     

PMN-PNN-PT陶瓷晶粒异常长大研究

采用两步法和等离子放电烧结技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷,对其高温热处理后晶粒异常长大进行了研究.发现添加5%(质量分数)过量PbO有助于晶粒的异常长大,观察到了3种典型的异常长大晶粒,为下一步固态法制备该组成单晶打下了基础.     

内耗频谱仪的应用及内耗频率峰机理的探讨

给出了自行研制的内耗频率谱仪的设计思想、工作原理、谱仪所达到的技术指标以及所测得的固体、颗粒物质．悬浮液等的内耗频率谱．从实验结果出发，讨论了内耗频率峰的机理．由颗粒物质或悬浮液加入倒摆的盛液筒后，扭摆系统共振频率升高(可由10^1--10^2Hz量级升至10^3Hz)和内耗频率峰的位置变化，可测得颗粒物质的熵力和组态熵能级的变化．从BaTiO3陶瓷在类二级相变温度时内耗的不稳定性和点阵失稳的相关性等，提出了固体中的内耗频率峰起源于切变振动诱发的晶格失稳和点阵熵的变化的观点．     

SiC_p/ZA27复合材料的摩擦磨损性能

探讨了不同含量、不同大小ＳｉＣｐ增强ＺＡ２７复合材料的摩擦磨损特性,并借助ＳＥＭ,ＥＤＡＸ对磨面及其剖面、磨屑进行了分析。结果表明：随着ＳｉＣｐ含量的增加,复合材料的磨损量急剧下降,摩擦系数也呈下降趋势,磨损机制将从粘着和剧烈切屑磨损转向微切削磨损;随着ＳｉＣｐ尺寸的增大,磨损量先急剧减小后趋于稳定,摩擦系数先减小后又升高,磨损机制将从粘着和剧烈切削转向微切削和因ＳｉＣｐ脱粘造成的磨料磨损;经ＸＲＤ分析复合材料的磨屑由Ｚｎ和Ａｌ的固溶体相及ＳｉＣｐ和对磨块４５＃钢的Ｆｅ相组成。     

PMN-PNN-PT单晶的固相法生长研究

采用两步法和埋入PMN-PT单晶为模板的等离子放电烧结（SPS）技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷，随后在1200℃下退火100h来诱导晶体的生长。实验结果表明，PMN-PNN-PT单晶〈111〉方向的生长速度明显快于〈001〉方向，而〈111〉方向生长的晶体形状为V字形，这是由钙钛矿结构的生长机理决定的，钙钛矿结构晶体的生长是通过〈001〉方向的层状生长来实现的。     

EFFECT OF AGING ON INTERNAL FRICTION,ELASTIC MODULUS AND MECHANICAL PROPERTIES OF TERNARY Mn-Cu-Al ALLOYS

Internal friction and elastic modulus of ternary Mn-Cu-Al alloys containing 56—60wt-% Mn,0-3.59 wt-% Al were measured with acoustic frequency,1 kHz,in the tempera-ture range of-150 to 150℃.It was found that when the specimen was aged in the temperaturerange under the spinodal curve within the miscibility gap(400—500℃),the internal fric-tion increases with an increase of the aging time and reaches a maximum value at a certain ag-ing time which is shorter with a higher aging temperature.Two internal friction peaks whichdid not appear before the aging were observed above room temperature after a definite agingtime.These are respectively the martensitic tranformation peak and the relaxation peak orig-inating from the stress-induced movement of the twin boundaries.The former peak shifts to-ward higher temperatures with an increase of the aging time,whereas the relaxation peak ap-pearing at 15℃,is independent of the aging time and temperature.The activation energy as-sociated with the relaxation peak was found to be 0.56 eV which is about the same as that ofthe relaxation peak in binary alloy containing 90 wt-% Mn.It was also found that thehardness,strength and the brittleness of the specimen increase when aged below the spinodalcurve within the miscibility gap.The addition or Al enhances the strength but reduces the in-ternal friction of the specimen.A choice of suitable aging time and temperature can give anoptimum compromise of high strength and high internal friction.Analysis of experimental re-sults suggests that spinodal decomposition leads to Mn-rich zones in the specimen and thuscauses the phase transformation and the change of mechanical properties of the specimen.     

时效对Mn-Cu-Al三元合金的内耗、杨氏模量和力学性能的影响

测量了Mn-Cu-Al三元合金(含56-60wt-％Mn,0-3.59wt-％Al)在-150—150℃的声频内耗,发现当试样在调幅线的温度范围内进行时效时,内耗随着时效时间的增加而增加,并在特定的时间内达到极大值.时效温度越高,达到极大值的时间越短.在时效一定的时间后出现马氏体相变峰和孪晶界面弛豫峰.相变峰随着时效时间的增加而向高温移动;弛豫峰则出现在15℃左右(频率约1kHz),测得其激活能是0.56eV. 在调幅线内时效使合金的硬度、强度及脆性墙加,Al元素有增加合金的强度而降低其内耗的作用.实验结果表明,在450℃时效2—3h,可得到合金的内耗和强度的最佳综合指标. 根据内耗、模量、金相检验和X射线分析的结果,认为调幅分解后产生的富Mn区是合金发生相变和高内耗的来源,也是合金的强度增加和韧性降低的原因.