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CHE 333 Class 23.

CHE 333 Class 23. Ceramics. Ceramic Structures. MIXTURES OF ELEMENTS Two Criteria for ceramic structures Electrical Neutrality using ionic charge cation (positive charge) must equal anion (negative charge) amounts. Eg NaCl Na one positive, Cl one negative

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CHE 333 Class 23.

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  1. CHE 333 Class 23. Ceramics

  2. Ceramic Structures MIXTURES OF ELEMENTS Two Criteria for ceramic structures • Electrical Neutrality using ionic charge cation (positive charge) must equal anion (negative charge) amounts. Eg NaCl Na one positive, Cl one negative 2. Cations (+ve) – usually smaller, contact Anions (-ve) in structure. Determines the coordination number of the structure for ceramics. Within certain ranges only particular coordination numbers will accommodate the different sized ions contacting each other.

  3. AX Ionic Structures NaCl structure CN 6 CsCl structure CN 8 ZnS structure CN 4 All these have a 1 to 1 cation to anion ratio, but different coordination numbers.

  4. AnXm and AnBmXp Structure Calcium Flouride CaF2 Barium Titanate Piezoelectric material

  5. Ceramic Structures

  6. Glass Silica Tetrehedra Tetrahedral Structure SiO44- Si – O ionic ratio is 0.29 tetra CN Unit cell of silicates. High Crystobalite 1470 to 1710C

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