Non-perovskite oxides

Other types of oxides, non-perovskite oxides including pyrochlores and fluorites, have also been investigated. It was found that the ammonia formation rates from pyrochlore-type membrane were close to that obtained from perovskite-type membranes, although in the case of the fluorite membrane, the formation rates were slightly higher (Liu et al., 2006 Xie et al., 2004 Wang et al., 2005). More comprehensive details about characteristics of each material, fabrication, cell components, and the formation rate can be found in a review presented by Amar et al. (2011). 

Proton Conductiyity in Selected Classes Of Non-Perovskite Oxides and Phosphates... 

The same general approach can be applied to grossly non-stoichiometric oxides [8], For an oxygen deficient perovskite such as SrFeC>2.5 this involves an explicit... 

These copper-oxide compounds crystallize in the perovskite structure and superconductivity is based on the (hole or electron) doping in the copper-oxide planes. This is the reason why these materials can be regarded as being 2D. The first compound of the family was La2 i Sr i Cu04 with Tc 38 K, which soon led to YBa2Cu307 5 with Tc — 92 K for 5 < 1 (Bums, 1993). The non-copper oxide electron-doped perovskite Bai-jcK cBiOa exhibits superconductivity near 30 K for 0.3 < X < 0.5 (Cavaeta/., 1988). 

Besides PTBs, A-site defective perovskite oxides are known to be formed when B = Ti. Nb.Ta and soon "13. Such compounds exhibit metallic properties and perovskite structures when the B atom occurs in a low oxidation stale. Compositions such as A0 5Nb03 (A = Ba. Pb etc.) where niobium is in the highest oxidation state adopt non-perovskite network structures. An interesting example20-21 of a A-site defective perovskite is Cu 5Ta03 which crystallizes in a pseudocubic perovskite structure. The unit cell is orthorhombic with a = 7.523, />= 7.525 and c = 7.520 A and eight formula units per cell. Tantalum atoms form... 

Other high-temperature superconductors can be described in similar fashion, e.g. Tl2Ca2Ba2Cu30io (containing Tl, Ca and Ba centres) is composed of layer sequence 27.4. The non-Cu02 oxide layers in the cuprate superconductors are isostructural with layers from an NaCl structure, and so the structures are sometimes described in terms of perovskite and rock salt layers. 

Despite the advantages of using CBED in powder characterization, due to the non-uniform thickness scattering effects can be produced which affect the diffraction patterns. The most frequent example is the information obtained from finely dispersed particles. As an example, the case of 10-50 nm YAG cubic particles of a YAIO3 perovskite oxide, YAP, in a strengthened alloy can be seen in [1]. 

Shimura, T., Fujimoto, S., Iwahara, H. (2001). Proton conduction in non-perovskite-t)fpe oxides at elevated temperatures. Solid State Ionics, 143, 117—123. 

The non-Cu02 oxide layers in the cuprate superconductors are isostructural with layers from an NaCl structure, and so the structures are sometimes described in terms of perovskite and rock salt layers. 

Eichel, R.-A., Kungl, H., and Jakes, P. (2013) Defect structure of non-stoichiometric and aliovalently doped perovskite oxides. Mater. TechnoL, 28, 241-246. 

Tlie plienomenon of half-metallicity has gained much interest in order to understand the unusual band structures in various classes of materials and their potential applications in future electronic devices. For example, zinc blend pnictides and chalcogenides e.g. CrAs) are another class of non-oxide materials (apart from Heuslers) in addition to the many oxide classes that are potentially half-metallic materials. Alkali metal doped rare earth oxomanganates, (REi- A MnOs), rutile-Cr02, spinel-Fe304 and Sr2peMo06 double perovskite oxide are examples of important half-metallic oxides. 

Proton solubility and conduction are known also for many non-perovskite classes of oxides, comprising mainly fluorite-related structures and structures with oxide ion tetrahedra. 

Oxygen Non-stoichiometry and Mixed Ionic-Electronic Transport in Perovskite Oxides... 

Apart from the perovskite oxides, some non-perovskite-type oxides also exhibit mixed oxygen ionic and electronic conducting properties and are used as the oxygen-separation membrane, which has been discussed in detail elsewhere (Liu et al, 2006). 

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