MME 3309 Lecture Notes - Lecture 17: Zirconium, Potential, Lanthanum Hexaboride
22 May 2017
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The tungsten filament in the field emitter lasts much longer than any other filament in the other two emitters; about 1 year or more. Thermionic emitter will often use tungsten or lanthanum hexaboride as cathodes. Lastly, schottky emitters utilize tungsten cathodes as well; however, these cathodes will often be coated with zirconium oxide: which emitters are used in the most expensive microscopes? (cost?) Since they provide a better resolution, higher magnifications, and longer cathode life, the field emitters are used in the most expensive microscopes, not to mention the higher quality vacuums associated with them. The price varies in the range of ,000 to ,000: which emitters are used in the least expensive microscopes? (cost?) Thermionic emitters are used in the most affordable scanning electron microscopes, tabletop.
