Chap 12 Solns-6E - CHAPTER 12 STRUCTURES AND PROPERTIES OF CERAMICS PROBLEM SOLUTIONS 12.5 This problem calls for us to predict crystal structures for

Chap 12 Solns-6E - CHAPTER 12 STRUCTURES AND PROPERTIES OF...

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CHAPTER 12 STRUCTURES AND PROPERTIES OF CERAMICS PROBLEM SOLUTIONS 12.5 This problem calls for us to predict crystal structures for several ceramic materials on the basis of ionic charge and ionic radii. (a) For CsI, from Table 12.3 r Cs + r I - = 0.170 nm 0.220 nm = 0.773 Now, from Table 12.2, the coordination number for each cation (Cs + ) is eight, and, using Table 12.4, the predicted crystal structure is cesium chloride. (b) For NiO, from Table 12.3 r Ni 2 + r O 2 - = 0.069 nm 0.140 nm = 0.493 The coordination number is six (Table 12.2), and the predicted crystal structure is sodium chloride (Table 12.4). (c) For KI, from Table 12.3 r K + r I - = 0.138 nm 0.220 nm = 0.627 The coordination number is six (Table 12.2), and the predicted crystal structure is sodium chloride (Table 12.4). (d) For NiS, from Table 12.3 r Ni 2 + r S 2 - = 0.069 nm 0.184 nm = 0.375 65
The coordination number is four (Table 12.2), and the predicted crystal structure is zinc blende (Table 12.4). 12.10 This question is concerned with the corundum crystal structure in terms of close-packed planes of anions.

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