Mixed metal oxides cuprates

In this chapter we have shown how critical the local structure is to the elucidation of the properties of mixed-ion oxides such as the CMR manganites, ferroelectric titanates, and superconducting cuprates. The effect of local structure is more pronounced for oxides than for free-electron metals since the local structure tends to be better defined in oxides due to their covalent bonding, relatively open structure, and the tendency for charge localization. In metals, on the other hand, small local effects are smeared out because of delocalized charge, strong screening, and densely packed structure. 

Here the general Bi A2A n iCun02n+2+mx formula of layered cuprates is used according to the layer sequence - (AO) - (BOx)m - (AO) - (CUO2) - (A Cu02)n-i - (AO) - (BOx)m -(AO) -, where 0alkali-earth or rare-earth cations, B - smaller cation, such as Bi " ". This reaction implies that copper oxidation state is unchanged. If fluorination does not occur via gas phase, i.e. if MF2 is mixed with the initial oxide, the final product will be contaminated with the metal oxide MO. 

Suspensions of HTSC for the electrophoretic deposition of bismuth [403-409] and thallium [403] HTSC, various cuprates of rare-earth metals and barium [204, 407,410-414], and also silver HTSC [415,416] and PbO-HTSC [417] compositions have been used. These are prepared in acetone, acetonitrile, toluene, butanol, methylethylketone, or mixed solvents. They contain chemically pure materials (silver is introduced as AgaO) dispersed thoroughly, first mechanically and then in liquid) by ultrasonic treatment (in which case the particles became charged). The choice of solvent is by and large determined by its effect on the stability of the deposited oxide [417]. 

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