Perovskite structure tripled

The incorporation of Cu ions in the perovskite structure is known for only a few examples since this particular structure is normally stabilized by or requires a B atom in a high formal oxidation state such as Ti4+ in BaTiOs, or Rhs+ in LaRhOs. Further, since Cu can not be readily stabilized in its Cu(m) state, and is unknown in the tetravalent state, the simple formation of ternary compounds such as LaCuOg or BaCuOs is not expected. Even in the K2NiF4 structure, the stabilization of Cu4+ as in Ba2Cu04 is not expected, but the formation of a stable Cu(II) state is a distinct possibility, as in La2Cu04. Copper(II), however, has been introduced in the doubled-or tripled-perovskite structure. Examples of these, which include structural distortions from cubic symmetry, are listed ... 

A Tripled-Perovskite — Relationship to the New High Tc Oxide Superconductor A tripled cell for the perovskite structure is shown in Figure 33. This structure is closely related to that of the new 90 K superconductor in the following way. The structure of the superconductor can be derived from a highly anion-defect, perovs-kite-type structure. The composition can be obtained as follows. 

The high-temperature superconductors are a remarkable set of materials that present us with fascinating scientific and technological challenges. The cuprate Ba2YCu307, the first material with a T > 77 K, has a tripled perovskite structure with Cu occupying the small perovskite B site while Ba and Y are ordered on the perovskite A site. Bulk crystals are key to... 

The compound Ba5[Ru2(0)n] has been synthesized by solid-state reactions of barium carbonate with ruthenium oxide. The X-ray structure shows that it contains peroxide ions and the ruthenium is in the +5 oxidation state, i.e., Ba5[Ru2(02)0g]. The novel mixed-valence Ru — Ru triple perovskites, Ba3M[Ru2(0)9] (M = Li, Na), have been grown from reactive hydroxide fluxes. ... 

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

Figure 38 Crystal structures of the A-site ordered double (a), LnBaT205, and triple (b) perovskites. Of particular interest is the occurrence of fivefold square-planar sites...

The compound I YCujOy shows an even higher superconducting transition ( 93 K) and crystallizes as a defect perovskite. The structure of I YCh Oy has been determined by neutron diffraction analysis. oThe space group is Pmmm with a = 3.8198, b = 3.8849 and c = 11.6762 A. Barium and yttrium are ordered on the A site to give a tripled cell along c and the oxygens occupy 7/9 of the anion sites. One third of the copper is in 4-fold coordination and 2/3 are five-fold coordinated (Gallagher, P.K. O Bryan, H.M. Sunshine,... 

Ca3Cu2C0304 phase has been obtained (Matveev et al. 1997) by a high-pressure synthesis, with crystal structure apparently of the triple-perovskite type [P4/mmm 384.2, 1033.6]. 2 = 47 K has been measured. 

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... 

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,... 

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