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51.
52.
Structures of the double perovskites Ba2M(II)M ′(VI)O6 (M=Ca, Sr, M′=Te, W, U) at room temperature have been investigated by the Rietveld method using X-ray and neutron powder diffraction data. For double perovskites with M=Sr, the observed space groups are I2/m (M′ =W) and (M′=Te), respectively. In the case of M=Ca, the space groups are either monoclinic P21/n (M′=U) or cubic (M′=W and Te). The tetragonal and orthorhombic symmetry reported earlier for Ba2SrTeO6 and Ba2CaUO6, respectively, were not observed. In addition, non-ambient X-ray diffraction data were collected and analyzed for Ba2SrWO6 and Ba2CaWO6 in the temperature range between 80 and 723 K. It was found that the rhombohedral structure exists in Ba2SrWO6 above room temperature between the monoclinic and the cubic structure, whereas the cubic Ba2CaWO6 undergoes a structural phase transition at low temperature to the tetragonal I4/m structure. 相似文献
53.
采用在聚(3,4-乙撑二氧噻吩)∶聚苯乙烯磺酸(Poly(3,4-ethylenedioxythiophene)∶Poly(styrenesulfonate),PEDOT∶PSS)阳极界面层上直接旋涂二甲基亚砜(Dimethyl Sulfoxide,DMSO)的方法,对PEDOT∶PSS薄膜进行修饰,以提高所制得的钙钛矿太阳能电池器件性能.在5000rpm转速条件下旋涂DMSO后,器件的能量转换效率达到11.43%,与PEDOT∶PSS阳极界面层未做任何修饰的器件相比,效率提高了29.15%.测试表征了修饰前后PEDOT∶PSS薄膜的透光性、表面形貌、电导率、器件的外量子效率曲线以及器件在光照和暗态下的J-V特性曲线,分析了器件性能提高的原因.结果表明:经过修饰的PEDOT∶PSS薄膜导电性显著增强,从而更加有利于器件阳极对空穴的抽取和收集;较未修饰时,器件的短路电流密度得到了大幅度提升,进而使得器件获得更高的能量转换效率. 相似文献
54.
稀土掺杂锰氧化物庞磁电阻效应 总被引:26,自引:0,他引:26
过去十多年来,具有庞磁电阻效应的稀土掺杂锰氧化物成为了凝聚态物理研究的重要领域。锰氧化物的载流子自旋极化率高,且在居里温度附近表现出很大的磁电阻效应,因此在自旋电子学中有潜在的应用前景。另一方面,锰氧化物是典型的强关联电子体系,它对目前有关强关联体系的认识提出了很大挑战。本文综述了锰氧化物的各种性质及其物理原因。全文首先概述了锰氧化物的庞磁电阻效应及其晶格和电子结构,简单介绍了其他一些庞磁电阻材料;随后综述了锰氧化物的电荷/轨道有序相及其输运性质;在第四部分简单介绍了锰氧化物中庞磁电阻效应的机制;最后讨论了锰氧化物的一些可能的应用,如低场磁电阻效应、磁隧道结、磁p-n结以及全钙钛矿的场效应管和自旋极化电子注入装置等。 相似文献
55.
The organic–inorganic hybrid perovskite CH3NH3PbI3 is becoming an interesting material in the field of energy harvesting. This material is one of the cleanest and cheapest components in solar cells which is available in ample amounts. However, most of the previous research work was done on thin film of this material. In the present work we describe the preparation of a powder containing nanoparticles of CH3NH3PbI3 using a sonochemical method. Characterization of the product was done by various methods, such as HRTEM, FTIR, PL, DLS and XRD. The particles were found to be highly crystalline (tetragonal crystal structure), polygonal in shape and having diameters of 10–40 nm. 相似文献
56.
Study of structural properties of (Ba0.5Sr0.5)PbO3 has been carried out in a wide temperature range from 10 to 1223 K using the X-ray powder diffraction technique. Two temperature-induced structural phase transitions at 948 and 1198 K have been found. For polycrystallines the XPS and electrical resistivity measurements have been performed. 相似文献
57.
Semiconductor materials have received substantial attention as photocatalysts for controlling water pollution. Among these materials, perovskite-structured SrSnO3 is a promising candidate for this application, whereas BaSnO3 exhibits very low activity. In the present work, Sr1−xBaxSnO3 (x = 0, 0.25, 0.50, 0.75 and 1) was synthesized by solid-state reaction and was applied in the photocatalytic discoloration of the organic dye Remazol Golden Yellow. The perovskite structure was obtained for all compositions of the solid solutions with both Sr2+ and Ba2+ present in the lattice. A remarkable change in the short-range symmetry was observed as the amount of Ba2+ increased, and this change led to a decrease in the band gap of the material. Although the BaSnO3 was not active toward water photolysis, the discoloration induced by this perovskite was twice that induced by SrSnO3. The two materials appear to feature different mechanisms of photodegradation: the direct mechanism prevails in the case of BaSnO3, whereas the indirect mechanism appears to play a key role in the case of SrSnO3. 相似文献
58.
J. Baszyński T. Toliński W. Kowalski A. Kowalczyk 《Czechoslovak Journal of Physics》2002,52(2):295-298
We studied the conductance of a point contact between a mechanically sharpened iron tip and a surface of the La0.7Sr0.3MnO3 perovskite electrode. The tip is fixed to a piezoelectric element and the conductance is measured as a function of the piezo voltage, which controls the tip pressing on the electrode. The height of steps between conductance plateaus is a multiple of the integer quantum e
2/h, characteristic for ferromagnetic materials in which the spin degeneracy is lifted. 相似文献
59.
A Perturbed Angular Correlation (PAC) study was performed on the system that presents a rich variety of structural and magnetic phase transitions as a function of the oxygen content (δ) or as a function of temperature (T). The PAC signal at room temperature allowed the determination of the Electrical Field Gradient (EFG) parameters and to correlate
them with the lattice average symmetry namely the orthorhombic (O′ or O*) Pbnm and rhombohedral (R) phases measured by X-ray diffraction. 相似文献
60.
Eric Quarez 《Journal of solid state chemistry》2003,176(1):137-150
The new Ba6Ru2Na2X2O17 (X=V, Mn) compounds have been prepared by electrosynthesis in molten NaOH and their crystal structures have been refined from single crystals X-ray diffraction, space group P63/mmc, Z=2, for X=V: , , R1=4.76%, for X=Mn : , , R1=3.48%. The crystal structure is a 12H-type perovskite with a (c′cchcc)2 stacking sequence of [BaO3]c, [BaO3]h and [BaO2]c′ layers. The tridimensional edifice is formed by blocks of Ru2O9 dimers that share corners with NaO6 octahedra. These blocks sandwich double sheets of X5+O4 tetrahedra. Several isotypic Ba6M5+2Na2X5+2O17 materials (X=V, Cr, Mn, P, As) and (M=Ru, Nb, Ta, Sb) have been prepared by solid state reaction and characterized by Rietveld analysis. The magnetic and electric properties have been investigated and show besides the Ru5+2O9 typical intradimer antiferromagnetic couplings, discrepancies of both χ and ρ versus T at 50 and 100 K for Ba6Ru2Na2X2O17 (X=V, As). In this work, a review of the identified Ru-hexagonal perovskite materials is also reported in order to overview the wide variety of possibilities in the field of new compounds synthesis. 相似文献