TEM研究La2／3Ca1／3MnO3中的畴结构

由于具有巨磁阻效应,La2/3Ca1/3MnO3 (LCMO)被广泛研究[1].LCMO是一典型的具有ABO3钙钛矿结构的化合物,其中La和Ca随机地占据A 位而Mn占据B位.在高温时, LCMO是立方相 (点群m3m,空间群Pm3m).LCMO的室温结构是正交相 (点群mmm,空间群Pnma).     

电光、热释电材料KTa_（1－x）Nb_xO_3的制备、性能及应用

介绍了电光、热释电材料ＫＴａ＿（１－ｘ）Ｎｂ＿ｘＯ＿３单晶、陶瓷、薄膜的制备方法，以及所制备材料的性能和应用。分析了其研究现状，简要论述了其发展趋势。     

BaxSr（1—x）TiO3多层膜椭偏光谱研究

用溶胶－凝胶技术在Bi(100）衬底上制备了单层和渐变型多层的BaxSr(1-X)TiO3薄膜，其膜层组分分别为：Ba0.7Sr0.3TiO3,Ba0.8Sr0.2TiO,Ba0.9Sr0.1TiO3,BaTiO3，对生长制备出的多层BaxSr(1-X)TiO3薄膜进行了变角度椭偏光谱测量，通过椭偏光谱解谱分析研究，首次得到了BaxSr(1-X)TiO3多层膜结构不同膜层的膜厚和光学常数，其结果显示：椭偏光谱分析得到的不同膜层的膜厚与卢瑟福背向散射测量得到的结果基本相符；渐变型多层膜中BaTiO3薄膜的折射率比单层BaTiO3薄膜折射率大许多，与体BaTiO3的折射率相接近，这说明渐变型多层膜中BaTiO3薄膜的光学性质与体材料的光学性质接近。     

La1-xSrxMnO3（X=0．1，0．2，0．3）薄膜的微观结构

具有钙钛矿结构的混价锰氧化物La1-xSrxMnO3是一种庞磁电阻材料。由于其在磁电阻存储器、读写磁头及各类磁传感器方面潜在的应用前景以及其丰富的物理内涵，一直引起人们的普遍关注。在过去的几年里，La1-xSrxMnO3薄膜以多种技术如脉冲激光沉积、MOCVD和磁控溅射等生长在不同基体上，     

Wet Etching Study of La0.67(Sr0.5Ca0.5)0.33MnO3 Films on Silicon Substrates

Wet etching of colossal magnetoresistive (CMR) perovskite La_0.67(Sr_0.5 Ca_0.5)_0.33MnO₃ (LSCMO) films on Bi₄Ti₃O₁₂/CeO₂/yttrium-stabilized zirconia (YSZ)-buffered Si substrates was investigated using potassium hydroxide (KOH) and buffered hydrofluoric acid (BHF) solutions. X-ray diffraction (XRD) and scanning spreading resistance microscopy (SSRM) measurements revealed that the morphological roughness of the LSCMO films increases, while the electrical resistance roughness decreases, with increasing KOH etching time. The LSCMO films are highly chemically resistant to KOH solution; however, in the case of BHF etching, an etch rate of 22 nm/min was obtained with high selectivity over a photoresist mask.     

La0.7Ca0.3MnO3多晶薄膜的sol-gel法制备及表征

以La、Ca、Mn的无机盐替代相应的醇盐,以冰乙酸为溶剂,乙酰丙酮(AcAc)为螯合剂,采用sol-gel法在Si(110)衬底上制备了La0.7Ca0.3MnO3(LCMO)多晶薄膜,并用FTIR、XRD、SEM、EDS和TEM等分析手段对薄膜进行了表征,通过不同磁场下电阻一温度(R-T)曲线,研究了样品的输运性质及...     

纳米La_(0.67)Sr_(0.33)MnO_3块体的磁性与电输运特性研究

采用溶胶–凝胶法制备了纳米La0.67Sr0.33MnO3样品,通过XRD、TEM及PPMS(物理性质测量系统)研究了样品的结构、磁性和电输运特性。结果表明,样品为单相菱方钙钛矿结构,平均晶粒大小为61 nm,在10 K到300 K间样品具有铁磁性和绝缘体导电行为,在温度小于60 K时因库仑阻塞效应样品电阻随温度降低急遽增加。纳米晶粒尺寸导致样品具有强的磁电阻效应,其中低场磁电阻效应由晶粒间自旋极化电子隧穿界面引起,高场磁电阻效应由界面磁无序引起。     

Vertical (La,Sr)MnO3 Nanorods from Track‐Etched Polymers Directly Buffering Substrates

A novel and general methodology for preparing vertical, complex‐oxide nanostructures from a sol–gel‐based polymer‐precursor solutions is developed using track‐etched polymers directly buffering substrates. This method is able to develop a nanostructure over the entire substrate, the dimensions and localization of the vertical nanostructures being preset by the polymeric nanotemplate. Thereby, nanostructures with lateral sizes in the range of 100 to 300 nm and up to 500 nm in height have been grown. Two examples are presented herein, the latter being the evolution of the initial, metastable nanostructure. Specifically, La_0.7Sr_0.3MnO₃ polycrystalline rods are grown at mild temperatures (800 °C); upon strong thermal activation (1000 °C) they suffer a profound transformation into vertical, single‐crystalline (La,Sr)_xO_y nanopyramids sitting on a La_0.7Sr_0.3MnO₃ epitaxial wetting layer. The driving force for this outstanding nanostructural evolution is the minimization of the total energy of the system, which is reached by reducing the grain‐boundary, total‐surface, and strain‐relaxation energies. Finally, advanced electron‐microscopy techniques are used to highlight the complex phase separation and structural transformations occurring when the metastable state is overcome.     

The effect of the signal-to-noise ratio in CBED patterns on the accuracy of lattice parameter determination

A method of higher-order Laue zone line position measurement in convergent-beam electron diffraction (CBED) is proposed based on Hough transformation. A thorough analysis of the errors introduced by this measurement procedure is performed and their influence on the accuracy of lattice parameter determination is estimated. A criterion is derived which enables the accuracy to be predicted before experimental measurements are made and, thus, allows the selection of the best CBED geometry for parameter measurement.     

Nanostructured thin films of the La0.7Sr0.3MnO3 manganite obtained using the extraction pyrolytic method

The extraction pyrolytic method is used to fabricate thin (100–300 nm) films of the lanthanum manganites La_0.7Sr_0.3MnO₃ on fused silica substrates. The films are deposited on the substrate using the alternate sessions of the centrifuging of solution and pyrolysis. The annealing of thin films at temperatures of greater than 650°C yields the single-phase La_0.7Sr_0.3MnO₃ material. It is demonstrated that the annealing temperature substantially affects the magnetic properties of the resulting films: the films exhibit the properties of spin glasses and ferromagnetic properties at temperatures of less than 700°C and greater than 700°C, respectively.     

(Pb,La)TiO3薄膜电畴生长的压电响应力显微镜研究

压电响应力显微镜为铁电薄膜电畴的研究提供了一种有效的检测方法.本实验用压电响应力显微镜(PFM)对不同退火温度的(Pb,La)TiO3铁电薄膜进行表征,得到了各个样品相应的形貌像、面外电畴像和面内电畴像.结果表明,随退火温度升高,(Pb,La)TiO3铁电薄膜的表面形貌表现出从粘连到结晶较好,到出现抱团的变化过程;此外,随退火温度升高,铁电薄膜的自发极化强度先增强后减弱.通过对这一系列铁电薄膜电畴进一步研究得到:在625℃退火1 h后,(Pb,La)TiO3铁电薄膜以非铁电相为主;而在650℃和675℃退火1 h后,(Pb,La)TiO3铁电薄膜以铁电相为主.     

锰掺杂对PZNT相结构和机电性能的影响

采用二步合成法制备了Pb(Zn1/3Nb2/3)0.20(Zr0.52Ti0.48)0.80O3+xMnO2压电陶瓷,探讨了不同剂量锰掺杂对陶瓷样品的相结构和机电性能的影响.结果表明,在1 200℃下烧结2 h,可得到处在准同型相界附近纯钙钛矿结构的压电陶瓷;随着MnO2掺杂量的增加,试样的压电常数d33和机电耦合系数kp先增大后减小,当掺杂w(MnO2)=0.2%时,d33和kp均达到最大值,分别为250 pC/N和0.52;而介电损耗tan δ持续下降,机械品质因数Qm则持续上升.当掺杂w(MnO2)=0.5%时,tan δ达到最小值,Qm达到最大值,其值分别为0.004 6和1434.