SrMnO3阻挡层对La0.8Sr0.2MnO3/Si异质结整流特性的改善

对用磁控溅射方法在硅基上直接沉积La0.8Sr0.2MnO3和引入SrMnO3(SMO)阻挡层后沉积La0.8Sr0.2MnO3进行了比较.对薄膜结构用X射线衍射试验表征,并分析了薄膜取向生长的原因.卢瑟福背散射实验结果表明,SMO阻挡层的引入显著地削弱了LSMO和Si界面层处的元素互扩散.电学测试表明LSMO/SMO/Si结构比LSMO/Si结构具有更好的p-n结整流特性,而且随SMO缓冲层的增厚,整流特性反而削弱.     

SrMnO3阻挡层对La0．8Sr0．2Mn03／Si异质结整流特性的改善

对用磁控溅射方法在硅基上直接沉积La0.8Sr0.2MnO，和引入SrMnO，（SMO）阻挡层后沉积La0.8Sr0.2MnO，进行了比较。对薄膜结构用X射线衍射试验表征，并分析了薄膜取向生长的原因。卢瑟福背散射实验结果表明，SMO阻挡层的引入显著地削弱了LSMO和si界面层处的元素互扩散。电学测试表明LSMO／SMO／Si结构比LSMO／Si结构具有更好的P—n结整流特性，而且随SMO缓冲层的增厚，整流特性反而削弱。     

取向对PLD法制备BiFeO3薄膜性能的影响

以快速等离子烧结法(SPS)制备的BiFeO3块体为靶材,用激光脉冲沉积(PLD)法在不同衬底上制备了BiFeO3(100)/LaNiO3(100)/Si(100)、BiFeO3(111)/LaNiO3(111)/SrTiO3(111)、BiFeO3(110)/Pt/TiO2/SiO2/Si、BiFeO3(110)LaNiO3(110)/Pt/TiO2/SiO2/Si不同择优取向的薄膜,并对薄膜进行了XRD和SEM分析。X射线衍射结果表明,BiFeO3薄膜外延沉积在导电层衬底上,并且它们具有相同的高度取向。SEM分析表明,薄膜上的晶粒是柱状形态,表面光滑致密且颗粒分布非常均匀,晶粒的边界和尺寸也能被清晰地观察到。通过铁电铁磁性能研究,BiFeO3(111)择优取向性能最佳。SrTiO3衬底上(111)取向的BiFeO3薄膜铁电剩余极化值达到了30.3μC/cm2,漏电流为1.0×10-3 A/cm2,饱和磁化强度为20.0kA/m。     

铁磁(La0.7Ca0.3MnO3)/高温超导（YBa2Cu3O7）双层薄膜微结构的高分辨电镜研究

采用脉冲激光沉积法在LaAlO3(LAO)衬底上生长了YBa2Cu3O7/La0.7Ca0.3MnO3(YBCO/LC-MO)和La0.7Ca0.3MnO3/YBa2Cu3O7(LCMO/YBCO)两种外延薄膜,利用高分辨电子显微镜研究了其微观结构。在YBCO/LCMO/LAO薄膜中,LCMO以层-岛模式生长,并形成层状取向畴结构。YBCO层均由c轴取向晶粒组成,其中含有c/3平移畴界、额外CuO层及Y2O3第二相等缺陷结构。在LCMO/YBCO/LAO薄膜中,LAO衬底上初始生长的YBCO为c轴取向,至一定厚度(几个纳米)转为c与a轴混合生长。LCMO层在YBCO上外延生长并具有[100]m与[011]m混合取向畴结构。在LCMO/YBCO界面未观察到失配位错,因此二者界面属应变型界面。     

多铁性BaTiO3/La2/3Sr1/3MnO3复合薄膜的制备及其强磁电效应的研究

使用脉冲激光沉积技术,在(001)取向的LaAlO3(LAO)单晶基片上外延生长了BaTiO3/La2/3Sr1/3MnO3(BTO/LSMO)双层复合薄膜.电学和磁学性能的研究显示复合薄膜具有较低的相对介电常数(εr=263),优良的铁电和铁磁性能以及高于室温的铁磁居里温度(Tc=317 K).复合薄膜的磁电电压系数(αE)为176 mV/A,高于同类结构磁电系统一个数量级,相应的界面耦合系数k值为0.68,表明铁磁层和铁电层界面之间存在较大程度的耦合.     

AlN/Si衬底上ZnO薄膜的择优取向生长

当ZnO薄膜直接沉积在Si衬底上时,由于ZnO与Si的晶格失配度大,不易于获得高质量的ZnO薄膜.因此,选择合适的衬底材料沉积ZnO薄膜,对提高其质量非常重要.本文采用射频磁控溅射法,通过在Si(100)衬底上预沉积AlN作为ZnO薄膜生长的缓冲层,获得了择优取向的ZnO薄膜.我们还讨论了ZnO薄膜在AlN/Si衬底上的取向生长机理.     

铁电相BiFeO3对多铁复合薄膜CoFe2O4-BiFeO3铁磁性能的影响

为了研究铁电相BiFeO₃对复合薄膜磁性能的影响,在LaNiO₃ (LNO)缓冲层的Si (100)衬底上旋涂制备了含有0、6、9、10层等不同厚度BiFeO₃的层状CoFe₂O₄-BiFeO₃ (CFO-BFO) 多铁复合薄膜。采用XRD、SEM以及TEM对其结构和形貌进行了表征,采用振动样品磁强计测量磁性,研究了不同厚度BFO对复合薄膜磁性的影响。结果表明: CFO和BFO在异质结构薄膜中共存。缓冲层LNO和铁磁相CFO薄膜具有精细微观结构及明显界面。铁电相BFO的厚度对CFO-BFO复合薄膜的磁性能产生了很大影响。在含有不同层数铁电相BFO的复合薄膜中,含有9层BFO复合薄膜的饱和磁化强度最大,达到了230 emu·cm^-3,相比无铁电相BFO的薄膜,饱和磁化强度提高了18.6%。初步讨论认为: 随着铁电相BFO厚度的增加,CFO与BFO之间的应力传导引起了复合薄膜饱和磁化强度的提高。     

Ag/Bi3.25La0.75Ti3O12/Bi4Ti3O12/Si结构铁电薄膜制备及其铁电性能的研究

利用溶胶-凝胶(sol-gel)方法,在硅基底上制备了Bi3.25La0.75Ti3O12/Bi4Ti3O12/Si铁电薄膜,其中Bi4Ti3O12作为缓冲层.用XRD方法分析了该结构铁电薄膜的物相结构;用扫描电镜对薄膜样品进行表面形貌观察;并且对该结构的铁电性能进行了研究.     

钙钛矿型氧化物SrTiO3/BaTiO3多层膜的激光分子束外延生长研究

用激光分子束外延技术在SrTiO3(001)衬底上外延生长SrTiO3/BaTiO3多层膜,通过反射式高能电子衍射(RHEED)原位实时监测并结合原子力显微镜(AFM),研究了不同基片温度下所生长薄膜的表面平整度,利用X射线衍射(XRD)对外延薄膜进行了结构分析,结果表明薄膜具有二维生长模式,在基片温度为380～470℃之间生长的薄膜具有原子级光滑,并且具有完全C轴取向.同时运用X射线光电子能谱(XPS)研究了薄膜界面的互扩散,结果表明降低制备薄膜时的基片温度有利于减少互扩散.     

La0.7Ca0.3MnO3薄膜微观结构的HRTEM表征

利用透射电子显微镜研究了衬底温度600～800℃条件下采用脉冲激光法在(001)LaAlO3(LAO)衬底上制备的La0.7Ca0.3MnO3(LCMO)薄膜的微观结构。结果表明薄膜由大量柱状晶组成且与LAO衬底形成良好外延关系。LCMO薄膜与LAO衬底的取向关系可以描述为:(ⅰ)(100)f∥(001)s、[011]f∥[100]s;(ⅱ)(011)f∥(001)s、[100]f∥[100]s。LCMO显示层状畴结构,即在衬底上初始生长的薄膜为(ⅱ)型畴,在此之上生长的薄膜为(ⅰ)类和(ⅱ)类型畴的混合体。薄膜中可观察到一些反向畴与孪晶等缺陷。薄膜与衬底界面少见错配位错,薄膜以Stranski-Krastanov模式生长。     

Flux growth of single magnetic sublattice antiferromagnetic garnets Ca3 Fe2 Ge3 O12 and Ca3 Mn2 Ge3 O12

Magnetic single crystals garnets Ca₃ X₂ Ge₃ O₁₂ with X = Mn³⁺ or Fe³⁺ containing Ca²⁺ and Ge⁴⁺ are of great interest due to the rise of an antifer-romagnetic order in one definite octahedral site. The optimal conditions for obtaining single magnetic-sublattice garnets of large size (1 cm in diameter) have been analyzed. Two groups of solvents have been tested: Bi₂ O₃ or PbO based flux. The best results were obtained with PbO flux and starting composition : % Moles 44 PbO 1b 35 GeO₂ 1b 15 CaO 1b 6 X₂ O₃.     

Thermal characterization of KClO3 KBrO3 and KIO3

The specific heats, thermal decompositions and thermal properties of the phase transitions in KClO₃ KBrO₃ and KIO₃ crystals were measured. The thermal stability of the compounds decreased in the order KIO₃ > KCIO₃ > KBrO₃. Over the temperature range 250–600 K, no phase transitions were detected for KBrO₃: one at 545 K for KClO₃ and two for KIO₃ at 345 and 487 K.     

Hydrothermal Crystallization in the Systems La2(CO3)3 ? 6H2O-CaCO3(BaCO3)-R-H2O (R = Na2CO3, K2CO3, NaHCO3, KHCO3, NaCl, NH4Cl, CO(NH2)2)

Crystallization in the systems La₂(CO₃)₃ ⋅ 6H₂O-CaCO₃(BaCO₃)-R-H₂O (R = Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃, NaCl, NH₄Cl, CO(NH₂)₂) was studied under hydrothermal conditions (400–450°C). The solid reaction products were found to contain LaOHCO₃ and NaLa(CO₃)₂. Detailed thermal decomposition schemes were proposed for these phases, and their lattice parameters were refined. __________ Translated from Neorganicheskie Materialy, Vol. 41, No. 11, 2005, pp. 1366–1372. Original Russian Text Copyright ? 2005 by Nikol'skaya, Dem'yanets.     

Electrical properties of sintered EuZrO3  EuNbO3 and EuNbO3

Electrical resistivity of two-phase products [yEuZrO₃ + (1 ? y) EuNbO₃] increased continuously with y, and a transition from a metallic to semiconducting characteristic occured at y = 0.14. The resistivity varied almost linearly with temperaure in the range y = 0 to y = 0.24, and thermal coefficients of resistivity at 300 K for the products decreased from +5.9 × 10^?4 K^?1 to ?7.4 × 10^?4 K^?1 according to the value of y. At y = 0.14, the thermal coefficient was almost zero. Thermal coefficients of electrical resistivity for the niobates with various oxygen contents were all positive in the range $\text{2.55 <}\text{O}\text{Nb}\text{< 3.24}$ and exhibited a sharp minimum at $\text{O}\text{Nb}\text{= 2.92}$. In all these niobates, Eu_xNbO₃ was a major phase and Eu₃NbO₆ or EuNbO₂ was detected as a second phase in the range $\text{O}\text{Nb}\text{> 3}$ or $\text{O}\text{Nb}\text{< 3}$ respectively. Peaks in the resistivity curves were correlated with a magnetic ordering temperature for samples with an overall ratio $\text{O}\text{Nb}\text{> 3}$.     

Influence of BaZrO3, MnCO3 additives on dielectric properties and microstructure of Ba(Zn1/3Nb2/3)O3 ceramics and Ba(Zn1/3Nb2/3)O3-Sr(Zn1/3Nb2/3)O3 solid solutions

The effect of BaZrO₃, MnCO₃ additives on the dielectric properties, sintering temperature and microstructure of Ba(Zn_1/3Nb_2/3)O₃ (BZN) and Ba(Zn_1/3Nb_2/3)O₃-Sr(Zn_1/3Nb_2/3)O₃ (BSZN) ceramics was studied in this paper. It indicates that both BaZrO₃ and MnCO₃ can lower the sintering temperature of the ceramics and accelerate the crystallization of BZN and BSZN. The dielectric constant ɛ _r increases after MnCO₃ added, but decreases when BaZrO₃ added alone. The existence of MnCO₃ can modulate the temperature coefficient of capacitance τ _c toward positive, while BaZrO₃, can make c more negative. MnCO₃ and BaZrO₃ can restrain the appearance of the second phase; while BaZrO₃, can prevent the appearance of the superstructure. In the BSZN system, when 1 mass % MnCO₃ added, sintering temperature(t _s ) is lowered to 1240°C. In this study, the best sample that has the excellent properties is sample 5 with dielectric properties of ɛ _r = 43.6, τ _c = −8 × 10⁻⁶ °C⁻¹ and tan δ = 0.6 × 10⁻⁴ (1 MHz). The sintering temperature of BZN and BSZN system can be lowered to less than 1300°C.     

Elastic modulus and hardness of CaTiO3, CaCu3Ti4O12 and CaTiO3/CaCu3Ti4O12 mixture

Three ceramic systems, CaTiO₃ (CTO), CaCu₃Ti₄O₁₂ (CCTO) and intermediate nonstoichiometric CaTiO₃/CaCu₃Ti₄O₁₂ mixtures (CTO.CCTO), were investigated and characterized. The ceramics were sintered at 1100 °C for 180 min. The surface morphology and structures were investigated by XRD and SEM. Elastic modulus and hardness of the surfaces were studied by instrumented indentation. It was observed that CCTO presented the higher mechanical properties (E = 256 GPa, hardness = 10.6 GPa), while CTO/CCTO mixture showed intermediate properties between CTO and CCTO.     

Electrical properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics modified with WO3

Ferroelectrics 0.67Pb (Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-PT) + x mol% WO₃ (x=0.1, 0.5, 1, 2) were prepared by columbite precursor method. Electrical properties of WO₃-modified ferroelectrics were investigated. X-ray diffraction (XRD) was used to identify crystal structure, and pyrochlore phase were observed in 0.67Pb (Mg_1/3Nb_2/3)O₃-0.33PbTiO₃+2 mol% WO₃. Dielectric peak temperature decreased with WO₃ doping, indicating that W⁶⁺ incorporated into PMN-PT lattice. Lattice constant, pyrochlore phase and grain size contribute to the variation of K_max. Both piezoelectric constant (d₃₃) and electromechanical coupling factors (k_p) were enhanced by doping 0.1 mol% WO₃, which results from the introduction of “soft” characteristics into PMN-PT, while further WO₃ addition was detrimental. We consider that the two factors, introduction of “soft” characteristics and the formation of pyrochlore phase, appear to act together to cause the variation of piezoelectric properties of 0.67PMN-0.33PT ceramics doping with WO₃.     

Deposition process of Si-B-C ceramics from CH3SiCl3/BCl3/H2 precursor

Si-B-C coatings have been prepared by chemical vapour deposition (CVD) from CH₃SiCl₃/BCl₃/H₂ precursor mixtures at low temperature (800-1050 °C) and reduced pressures (2, 5, 12 kPa). The kinetics (including apparent activation energy and reaction orders) related to the deposition process were determined within the regime controlled by chemical reactions. A wide range of coatings, prepared in various CVD conditions, were characterized in terms of morphology (scanning electron microscopy), structure (transmission electron microscopy, Raman spectroscopy) and elemental composition (Auger electron spectroscopy). On the basis of an in-situ gas phase analysis by Fourier transform infrared spectroscopy and in agreement with a previous study on the B-C system, the HBCl₂ species was identified as an effective precursor of the boron element. H_xSiCl_(4−x), SiCl₄ and CH₄, derived from CH₃SiCl₃, were also shown to be involved in the homogeneous and the heterogeneous reactions generating silicon and carbon in the coating. A correlation between the various experimental approaches has supported a discussion on the chemical steps involved in the deposition process.     

(La2/3Ca1/3)(Mn(3-x)/3Fex/3)O3体系磁电阻行为的研究

通过系统地测量(La     

Verres mixtes LiPO3ZnCl2 et LiPO3AlCl3 conductivite electrique; approche structurale

Following our attemps of comparisons between the glasses containing AgPO₃ and the glasses containing LiPO₃, data on the glass transition temperatures, the electrical conductivities and Raman spectra of the LiPO₃ZnCl₂ and LiPO₃AlCl₃ glasses are reported. A mechanism of exchange of ions has been already proposed to explain the properties of the AgPO₃MI₂ (with M = Pb, Cd, Sr, Hg) and AgPO₃MI (with M = Na, K) glasses. Such an hypothesis does not agree with the properties of the LiPO₃ZnCl₂ glasses but seems to be still valid for the LiPO₃AlCl₃ glasses.