Material science Key theory

What is the difference between an atomic structure and a crystal structure?

Atomic structure describes the arrangement of particles inside a single atom  where as in an crystal structure the multiple atoms are ordered together in a neat geometric pattern.

Explain why properties of polycrystalline materials are most often isotropic.

1.      Polycrystalline materials are made out of many small randomly placed crystal structures, their directional effects thus average out leaving no net effect. Thus they are isotropic.

: For a ceramic compound, what are the two characteristics of the component ions that determine the crystal structure

The electrical charges and their radii

The zinc blend crystal structure is one that may be generated from close-packed planes of anions.
 a) Explain what crystal structure the stacking sequence for this structure will be?
 b) Explain whether the cations will fill the tetrahedral or octahedral positions?

a) The stacking sequence is ABCABC and thus FCC structure.
b) Tetrahedral since the cation wants to be surrounded by 4 anions.