MATE 210 Section 1 Crystalline Structure CERAMICS (Smith: Chapter 11.1-11.3) The term ceramic comes from Greek ( keramikos ) “burnt stuff” ….often form ceramics by high temp heat treatment process called firing….
MATE 210 Ceramic Structures- compounds b/w metal and nonmetal ions rather than atoms: + cations- anions- ionic bonds - more complex structures than metals more covalent more ionic 2 types of ions
MATE 210 • Charge Neutrality :--Net charge in the structure should be zero.--General form: A m X p m, p determined by charge neutrality CaF 2 : Ca 2+ cation F-F-anions + AX – Zinc Blende, NaCl, CsCl AX 2 – Flourite ABX 3-- Perovskite
MATE 210 • Coordination # increases with Issue: How many anions can you arrange around a cation? r cation r anion r cation r anion Coord # < .155 .155-.225 .225-.414 .414-.732 .732-1.0 ZnS (zincblende) NaCl (sodium chloride) CsCl (cesium chloride) 2 3 4 6 8 COORDINATION # & IONIC RADII
Bonus Problem • What type of crystal structures would Ca x F y , Ca x O y x As y form?
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