Ruddlesden-Popper

The superconducting oxides include both perovskites and Ruddlesden-Popper compounds which have an orthorhombic arrangement of cubic cells, alternatively of the perovskite and sodium chloride structures. The common feature of all of these is the presence of copper as a major component. The first ceramic superconductor was a lanthanum-strontium substituted cuprate (Lai Sr Cu04 z), which is a perovskite, but subsequently the inter-oxide compound Y203 2BaO 3CuO, commonly referred to as a 123 compound, was shown to have superior performance. The speculation concerning the conduction mechanism is that this involves either Cu3+-Cu2+ positive hole... 

Shimizu K, Itoh S, Hatamachi T, Kodama T, Sato M, Toda K (2005) Photocatalytic water splitting on Ni-intercalated Ruddlesden-Popper type H2La2/3Ta207. Chem Mater 17 5161-5166... 

The photocatalytic cleavage of water in the Dion-Jacobson series is presented first followed by studies on Ruddlesden-Popper series and finally on the intermediate series. Table 16.3 lists the oxides employed for photocatalysis studies. 

K2La2Ti3Oio is a typical oxide in the Ruddlesden-Popper series exhibiting interlayer reactivity44) It forms a hydrate with about 1-2 H20 molecules per formula unit under ambient conditions.44,74) Fig. 16.9 shows schematic structures of anhydrous and hydrated oxides. Variation of the number of waters of hydration with humidity and exposure time has been reported for the analogous compound K2Nd2Ti3O10.70) A band gap of 3.5 eV has been estimated for K2La2Ti3Oi0 from reflectance measurements.102)... 

Figure 15.22 (a) The Ruddlesden-Popper (RP) series An+1Bn03n+1 can be viewed as an assembly... 

The cubic AMO3 perovskite structure consists of an MO3 array of comer-shared MO6/2 octahedra with a large A cation at the body-center position. As is illustrated in tig. 1, this structure allows formation of the Ruddlesden-Popper (1957,1958) rock-salt/perovskite intergrowth structures MO (AMO3 ) . In all these structures, the mismatch between the equilibrium (A-O) and (M-O) bond lengths is given by the deviation from unity of the geometric tolerance factor... 

Fig. 1. (a) The ideal cubic perovskite structure and (b) the n = 1 Ruddlesden-Popper phase AO AMO3. 

Figure 5.10. A layer of octahedra sharing vertices in only two dimensions, as might be found, for example, in perovskite intergrowths like the Ruddlesden-Popper oxides. The axial and equatorial oxygen atoms are not equivalent in that the former belong to single octahedra, whereas the latter are in bridging positions, shared by two octahedra.

It was pointed out in the introduction to this chapter that an experimental criterion for metallicity is the observation of a positive temperature coefficient to the electrical resistivity. The so-called bad or marginal metals are those that meet this criterion, but in which the value for the resistivity is relatively high (p > 10 flcm). Many transition metal oxides behave in this manner, while others (e.g. ReOs and RuOa) have very low electrical resistivities, similar in scale to those of conventional metals (p < 10 " O cm). Consider the Ruddlesden-Popper mthenates. Both strong Ru 4d-0 2p hybridization and weaker intrasite correlation effects compared to the 3d transition metals are... 

K3M2F7 or Ruddlesden-Popper-type. If in the perovskite structure AMF3 the layer separation by addition of AF is performed every second layer only, the double-layer stmeture type K-iNi2 Fq is obtained, known in oxides as Sr3Ti207 or Ruddlesden-Popper stmeture (s.g. I4/mmm, Figure 21(b)). 

Compounds Containing Perovsldte Layers. A second class of layered oxides have structures related to the three-dimensional perovsldte lattice and include the Auriv-iUius phases, the Ruddlesden Popper phases and the Dion-Jacobson phases. The general composition can be written M [A iB 03 +i] where A is an alkaline or rare earth metal, and B is niobium or titanium. In the AurivUhus phases M = Bi202 +, whereas M is an aUcah metal cation in the ion-exchangeable Ruddlesden Popper a = 2) and Dion-Jacobson a = 1) phases. The relationships between the three structure types is shown in Figure 14. The intercalation chemistry of the Dion Jacobson phases was the first to be studied. 

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

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