Triple perovskite layers

Figure 4 a,b,c Crystal stmcture of cuprates characterized by single rock salt layers (n=l) (a) m=l member, (b) m=2 member, (c) m=3 member (the stmcture of this member which corresponds to the oxide BaPbYSrCusOg differs from the general description by the location of oxygen vacancies in one sheet of the triple perovskite layer). 

Figure 18 (a) Idealized model of the translation of the triple perovskite layers along die c axis, (b) Example of possible sites for additional oxygen at the domain boundary. 

RSr2Cu307(Ce02)2, containing double fluorite imits (see sect. 3) which are interleaved with the cuprate triple-perovskite layers (see sect. 13) (Wada et al. 1990a). As an example (Hoo.33Ceo.67)3Sr2Cu30ii [P4/mmnv, 382.4(1), 1722(1)]. 

As a representative example, the crystal structure of YBaiCusOe + M. contains cuprate triple-perovskite layers formed by linear w = 0) or square-planar (w = 1) coordinations... 

Eu4Ti30,o appears to be the only documented rare earth oxide phase likely to have n = 3 in the Ruddlesden-Popper series (McCarthy et al., 1969). In accord with the above structures it consists simply of triple perovskite layers translated with respect to each other as before. 

An alternative strategy retaining some of the characteristics of perovskite may be to look towards related materials with structural features that would promote both ionic and electronic conduction. There are clear routes to achieving this with the obvious choices being the layered perovskites with the A2BO4 structure type or the double and triple perovskite materials. With the former, investigation of interstitial conduction mechanisms is essential whilst with the latter there is debate about the effect of order/disorder of the oxygen lattice sites. Each of these structural types will be considered in subsequent sections. 

A further extension of the concept of developing layered perovskites leads to the consideration of double (AA B205+j) and triple perovskites. In the context of fuel cell electrodes the first double perovskite to be investigated was GdBaCo205+j (GBCO) which adopts orthorhombic symmetry, in which Co ions order in square... 

Materials for Next Generation SOFCs relates two important strategies for improving fuel cell performance. The first section covers a nano-engineering solution, to produce thin layers to get surface (interfacial) ionic conductivity. The second section covers the use of new electrode materials based on Perovskite-related phases, Ruddleston-Popper phases, and double and triple perovskites. 

Figure 14 The triple layer structures of the Aurivilius, Ruddlesden-Popper, and Dion-Jacobson perovskite phases...

Figure 10 Projection of twinning domains in a crystal. The change in the orientation of the Cu04 groups is observed in one perovskite triple layer.

Upon reaction with a bulky organic base such as tetra-( -butyl)ammonium hydroxide (TBAX)H ), the proton forms of many-layered perovskites exfoliate into colloidal sheets. For example, in perovksite-related layer phases, HCa2Na 3Nb 03 , a surfactant molecule with an amine head group is first intercalated by protonation. The surfactant generally has a hydrophilic polyether tail, which enhances the intercalation of solvent molecules. Stable dispersions in water and other polar solvents have thus been obtained [35]. Triple-layer Dion-Jacobson phase HCa2Nb30,(, exfoliates into TBA Hj Ca2Nb30jj sheets upon reaction with TBA OH" (Fig. 10.2.3) [36]. 

Single, double or triple peiuvskite-like blocks between successive [FCjAs p layers in Fe2As2/perovskite materials... 

Machida, M., Mitsuyama, T., Ikeue, K., Matsushima, S., and Arai, M. (2005) Photocatalytic property and electronic structure of triple-layered perovskite tantalates, MCa2Ta30io (M=Cs, Na, H, and C6H13NH3)./. Phys. Chem. B,... 

Figure 25. The reaction lines for the formation of different types of the layered perovskite-like oxides, a - double-layered Ruddlesden-Popper aluminates b - double-layered Ruddlesden-Popper manganites c - double-layered Ruddlesden-Popper ferrites d - double-layered Aurivillius phases e - single- and triple-layered Ruddlesden-Popper titanates.

Lalena, J.N., Falster, A.U., Simmons, W.B., Carpenter, E.E. Synthesis and characterization of new mixed-metal triple-layered perovskites, Na2La2Ti3 xRuxOio (x < 1.0). Chemistry of Materials. 2000, 12, 2418-2423. 

---