Lecture 3 - Semiconductors, superconductors and catalysts

From the programme:

A metal such as copper, in marked contrast to an insulator such as mica, conducts electricity freely, and its resistance drops with decreasing temperature. But some crystals, as Faraday discovered in 1839 have intermediate powers of conduction, and their resistance decreases with increasing temperature. These are the so-called semiconductors, nowadays the key components of sophisticated electronic circuits. Some other crystals exhibit the remarkable phenomenon, currently of exceptional and world-wide interest, of losing all their resistance as the temperature drops. These are the superconductors. We shall demonstrate how they could revolutionize fields as distinct as medical diagnostics and transportation.

 Semiconductors often respond ultra sensitively to light, a fact that is put to good use in the construction of both radiation detectors and solar cells and in the production of infrared cameras. Semiconductors, when appropriately designed in both the chemical and engineering sense, can also function as efficient lasers.

Catalysts are capable of effecting highly efficient chemical conversions and, depending upon the reaction in question, a crystalline catalyst may be a metal, a semiconductor, or an insulator. We shall illustrate the remarkable performance of two particular crystalline catalysts: platinum and a man-made version of minerals known as zeolites.






John Meurig Thomas and David Phillips



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