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General Chemistry Principles, Patterns, and Applications, 2011

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(a)<br />

Stacking three unit cells of the Ca-centered CaTiO3 perovskite structure (part (b) in ) together with<br />

(b) replacement of all Ti atoms by Cu, replacement of Ca in the top <strong>and</strong> bottom cubes by Ba, <strong>and</strong><br />

replacement of Ca in the central cube by Y gives a YBa2Cu3O9 stoichiometry. (c) The removal of two<br />

oxygen atoms per unit cell gives the nominal YBa2Cu3O7 stoichiometry of the superconducting<br />

material.<br />

lists the ideal compositions of some of the known high-temperature superconductors that have been<br />

discovered in recent years. Engineers have learned how to process the brittle polycrystalline 1-2-3 <strong>and</strong><br />

related compounds into wires, tapes, <strong>and</strong> films that can carry enormous electrical currents. Commercial<br />

applications include their use in infrared sensors <strong>and</strong> in analog signal processing <strong>and</strong> microwave devices.<br />

Table 12.7 The Composition of Various Superconductors<br />

Compound<br />

Tc (K)<br />

Ba(Pb1−xBix)O3 13.5<br />

(La2−xSrx)CuO4 35<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

1151

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