Double perovskite layers

Hexagonal. Face-sharing, infinite chains of [MnQj] <7 d discrete [MnC f tetrahedra Tetragonal (lAjmm). Double perovskite layers, with each [MnClj] sharing five comers Cubic inverse spinel [MnClj]... 

Figure 30 (a) [010] image of an original defect observed in TlBa2NdCu207. Symbols are DP for the Double Perovskite layers, three small arrows for the BaO-HO-BaO layers and F in a square bracket for the structural unit (Nd2Cu206). (b) Schematic representation of the image contrast. The sizes of the white spots are not strictly proportional to those observed in the experimental image they only indicate the nature of the different rows. 

The mechanism of formation of the double-perovskite layered aluminates was investigated for the series of Ln2SrAl20y (Ln=La, Nd, Sm, Eu, Gd, Ho) [61-65,29] in the temperature range of 1000-1500°C for the reaction of the binary oxides and strontium carbonate ... 

Formation of the Double-perovskite Layered MANGANITES LN2SRMN2O7 (Ln=La, Nd, Gd). 

Similarly to the case of direct-oxidation anode materials, sulfur-tolerant anode materials based on sulfides [6, 7] or double-perovskite oxides have special requirements for their processing into SOFC layers. For example, nickel sulfide-promoted molybdenum sulfide is tolerant to high sulfur levels [7], However, it has a low melting temperature [6] that has resulted in the development of cobalt sulfide as a stabilizer of the molybdenum sulfide catalyst [6], CoS-MoS2 admixed with Ag has an even higher performance in H2S-containing fuels than in pure H2 [6]. However, processing methods such as PS, infiltration, or sol-gel techniques that can process... 

Figure 24m HREM image of a characteristic defect, an extra row of atoms appears in the perovskite layer such a defect is interpreted by the existence of a double row of edge sharing Cu04...

The fundamental structure of Bi2Sr2CaCu20g (or the 2212 phase), ignoring the modulations, is orthorhombic, with a = 5.39 A, = 5.41 A and c = 30.8 A. A schematic diagram of the structure is shown in figure 6.4(a). It consists of a Bi202 double layer and a perovskite layer containing two Cu02,... 

I. Zvereva et al., Complex aluminates RE2SrA1207 (RE = La, Nd, Sm-Ho) Cation ordering and stability of the double perovskite slab-rocksalt layer P-2/RS intergrowth. Solid State Sci. 5(2), 343-349 (2003). 

A novel system was introduced to the catalytic field by Matsuda et al. (1993). A solid of the general formula ALaNb207 is made up of the layer compound LaNb207 with double perovskite structure interleaved with A atoms. If the interlayer compound is water, they call the compound HLa2Nb707 to indicate the acidic character of this system. They report the results obtained when 1- and 2-butanol were reacted over this solid at temperatures between 453 and 623 K. The secondary alcohol was much more reactive, as expected for an acid catalyst. Consistent with this, no dehydrogenation product was formed when... 

Many other reactions could be illustrated, including the formation of ordered phases with n, stacking of perovskite slabs, ordered stacking of perovskite slabs and brucite-type double hydroxide layers or perovskite blocks with no interlayer cations present. For further information on the stmctural chemistry of these complex reactions, see Further Reading. 

The A-site ordered double perovskite (Nag jKg jlBajBi Ojj has a superconducting transition temperature T of approximately 27 K. Tlie structure is cubic, space group Imlm (229), a=0.8550nm, with ordering of the (Na, K) and Ba atoms in layers to give a doubled perovskite unit cell. As the formula suggests, one set of A-sites (Al) is only partially occupied and contains the Na " and K " cations and a... 

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