Influence of low trivalent iron doping on the electrical characteristics of PZT

Piezoelectric materials based on lead zirconium titanium oxide with a composition near the morphotropic phase boundary, (Pb_0.94Sr_0.06)(Zr_0.53Ti_0.47)O₃[PSZT] have been synthesized by sol–gel method. The influence of B-site aliovalent dopant Fe³⁺ on the structure, ferroelectric, dielectric, piezoelectric characteristics and microstructure have been investigated. The influence of the transition metal–oxygen vacancy defect-dipoles on the electrical characteristics have also been investigated.     

A-and B-site solubilities of trivalent rare-earth cations and B-site cation ordering in lead magnesium niobate

The solubility limits of trivalent rare-earth cations of widely different ionic radii on the A and B sites of lead magnesium niobate (PMN) have been determined. The yttrium, magnesium, and niobium cations in yttrium-doped PMN have been shown to be 1: 1 ordered on the B site. The ordering has been studied using computer modeling, both with and without allowance for Pb vacancies on the A site. The dielectric properties of the trivalently doped PMN ceramics have been investigated.     

掺杂稀土元素对BaTiO3系统介电性能的影响

研究了稀土氧化物Sm2O3及Gd2O3的掺杂对细晶BaTiO3系统介电性能的影响.稀土添加剂Sm2O3的掺杂可以形成化学均匀性系统,对居里峰有明显的改善作用;Gd2O3的掺杂可以形成化学非均匀性系统即壳-芯结构,这可以使细晶BaTiO3系统获得理想的介电性能,满足X7R特性.     

BiFeO3 films doped in the A or B sites: effects on the structural and morphological properties

Metal-Organic Chemical Vapor Deposition (MOCVD) has been applied to the fabrication of BiFeO3 films undoped and doped with Ba or Ti on SrTiO3 (100) and YSZ (100) substrates. The films have been deposited using a multi-metal source, consisting of the Bi(phenyl)3, Fe(tmhd)3 and Ba(hfa)2 tetraglyme or Ti(tmhd)2(O-iPr)2 (phenyl = -C6H5, H-tmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = iso-propoxide; H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = CH3O(CH2CH2O)4CH3) precursor mixture. The structural and morphological characterization of films has been carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Chemical compositional studies have been performed by energy dispersive X-ray (EDX) analysis. Structural and morphological characterizations point to the formation of homogeneous and flat surfaces for both undoped and doped BiFeO3 films.     

Comparison of the effectiveness of rare-earth sintering additives on the high-temperature stability of α-sialon ceramics

α-sialon starting compositions withm=1 andn=1.7 have been densified by either hot-pressing or pressureless sintering using Y₂O₃ and Ln₂O₃ additions where Ln is neodymium, samarium, dysprosium or ytterbium. The resulting materials have been heat treated at 1450°C to crystallize the grain-boundary liquid into crystalline oxynitride phases. The effect of sintering additive on the design of final properties has been studied and Dy₂O₃ was found to be the best sintering additive to obtain desirable properties for α-sialon and also α-β sialon materials.     

Modeling of trivalent chromium speciation in binding sites of marine macroalgae Sargassum Cymosum

In this study, the marine macroalgae Sargassum cymosum was used for the purification of waters contaminated with trivalent chromium. FTIR analysis revealed a high heterogeneity of the biosorbent surface, as indicated by the different absorption peaks. Biomass titration revealed two main functional groups, carboxylic and hydroxyl. The pK_1,H value and the number of carboxylic groups were estimated as 3.05 ± 0.01 and 1.90 ± 0.01 mmol g^?1, respectively. An equilibrium model considering the metal speciation in aqueous solution was able to predict the experimental data at different pH values. Adsorption of chromium increases significantly with an increase of the solution pH. Furthermore, the speciation of the binding sites as a function of the solution pH was predicted, showing that Cr(OH)²⁺ has a higher affinity than Cr³⁺ to the binding sites. A mass transfer model considering an intraparticle diffusion resistance was able to predict the kinetic data, showing that Cr³⁺ diffuses faster that CrOH²⁺.     

Thermodynamic magnetization discontinuity between the A and B phases of superfluid3he

We present data for the magnitude of the thermodynamic magnetization discontinuity at the equilibrium A-B transition in superfluid³He, M_AB, over its entire pressure-temperature-magnetic field phase diagram. The data was taken by measuring flux changes in a SQUID pick-up coil, which was calibrated by a novel first-principles technique. We compare our results with those of NMR experiments, and find that the two types of measurements yield different values, and this discrepancy is not the result of thermometry or field errors.     

Solitonic lattice and Yukawa forces in the rare-earth orthoferrite TbFeO3

The random fluctuations of spins give rise to many interesting physical phenomena, such as the 'order-from-disorder' arising in frustrated magnets and unconventional Cooper pairing in magnetic superconductors. Here we show that the exchange of spin waves between extended topological defects, such as domain walls, can result in novel magnetic states. We report the discovery of an unusual incommensurate phase in the orthoferrite TbFeO(3) using neutron diffraction under an applied magnetic field. The magnetic modulation has a very long period of 340?? at 3?K and exhibits an anomalously large number of higher-order harmonics. These domain walls are formed by Ising-like Tb spins. They interact by exchanging magnons propagating through the Fe magnetic sublattice. The resulting force between the domain walls has a rather long range that determines the period of the incommensurate state and is analogous to the pion-mediated Yukawa interaction between protons and neutrons in nuclei.     

Sintering of Si3N4 in the presence of additives from Y2O3-SiO2-Al2O3 system

The sintering process of Si₃N₄ in the presence of a liquid phase from the Y₂O₃-SiO₂-Al₂O₃ system was investigated. The starting composition of liquid phase was varied according to data in the phase diagram of the Y₂O₃-SiO₂-Al₂O₃ system, in order to lower the temperature of liquid formation because it might exhibit an influence on the sintering behaviour of Si₃N₄. Densification as well as phase analysis were followed as a function of composition and the amount of liquid phase, both in the sintered and in hot pressed samples.     

Tolerance factor and the stability discussion of ABO3-type ilmenite

The tolerance factor of ABO₃-type ilmenite by analyzing the ABO₃ ilmenite crystal structure is established. Combining with the electronegativity difference and octahedral factor of ABO₃ structure, regularities governing the formation and the stability of ilmenite-type compounds are discussed. The tolerance factor equation was proved appropriate for ilmenite structure by analyzing the structure stability of some ilmenite compounds. According to the results of statistically analyzing the tolerance factor and electronegativity difference of the present ABO₃-type ilmenite, the experience tolerance factor value and experience electronegativity difference value to form stable ilmenite compound were obtained, that is, t > 0.80 and e > 1.465, and the lowest limit of the octahedral factor for ilmenite formation is 0.48.     

Surface energy and textural boundary conditions between A and B phases of 3He

The behavior of the order parameter A _ai (x) is investigated for a planar interface between ³He-A and ³He-B. Boundary conditions are derived and the surface energy is calculated in excellent agreement with experiment. Our energy is 30% lower than a previous estimate which assumed the presence of a planar phase in the transition region.Alexander von Humboldt Fellow.     

Impure zirconia electrical conductivity enhancement by rare-earth minority ions in the Y2O3 RE2O3 ZrO2 system

Impure zirconia stabilized by 12 wt% yttria concentrate (85 wt% Y₂O₃ + 15 wt% rare-earth (RE)) was found to have high grain and grain-boundary electrical conductivities. The influence of the RE on the segregation of impurities was studied for four different compositions. Microstructure features are evidence for the enhanced segregation of impurities due to RE ions. The increased grain and grain-boundary conductivities are a consequence of the segregation of impurities.     

The performance and applications of PZT composite transducer with 3-3 connectivity

The performance of 3-3 connectivity composite piezoelectric transducers is discussed. This type of transducer has been successfully used in ultrasonic imaging (frequency range: 150~600 kHz). Using a simple hardware system, this type of transducer can recognize a very thin aluminum plank (6 mm in thickness) in water, and it can clearly recognize a multilayer body.     

PZT陶瓷中由氧空位与畴壁相互作用引起的内耗

采用低频倒置扭摆内耗仪对组分为 Pb(Zr0.7Ti0.3)O3 (PZT73)和 Pb(Zr0.3Ti0.7)O3 (PZT37) 的两种陶瓷的内耗 Q-1及振动频率的平方 f 2（正比于材料的剪切模量 G）与温度的关系进行了 测定。在纯三角相的 PZT73陶瓷中发现两个内耗峰。高温内耗峰 PM起源于材料的顺电－铁 电相变 ,低温内耗峰 P1本质上是一个宽化的 Debye峰,可归因于氧空位作用下的畴壁振荡弛豫。 对纯四方相的 PZT37陶瓷,除了 P1和 PM峰外,在 P1与 PM峰之间另有内耗峰 P2,这与 900畴附 近的氧空位团簇的弛豫有关 ,其特征可用描述强关联系统的关联态模型（ Coupling model）描述。     

ABO3型氧化物的结构与性能及其应用

总结了ABO3型氧化物可能具有的各种晶体结构类型，以及由此产生的宏观电、光、声学性能。讨论了ABO3型功能晶体和具有ABO3型结构主晶相的功能陶瓷材料在现代电子信息、航空航天、国防军事等领域的应用与前景。     

BaTiO3—R2O3—MgO系介质的稀土掺杂效应

研究了BaTiO03-R2O3-MgO(R=La,Ce,Pr,Nd,Sm,Gd,Dy,Ho,Y,Er,Yb)系介质的稀土掺杂效应.结果表明,大半径稀土离子在BaTiO3中形成元素均匀性分布,并促进晶粒的长大;而小半径稀土离子能产生明显的细晶效应,在晶界局部富集而偏析出现焦绿石型第二相晶粒R2Ti2O7.随着镧系收缩,稀土掺杂BaTiO3陶瓷的绝缘电阻率明显提高,而稀土离子在BaTiO3中的固溶度大致呈降低趋势.大半径稀土掺杂材料的ε-T曲线呈现单峰效应且居里点下移,而小半径稀土掺杂材料为双峰效应且居里点上升,△C/C-T稳定性显著提高达到X8R.