Page 94 - Materials Chemistry, Second Edition

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2.3. The Crystalline State

Grain Boundary

Lattice
spacing/orientation

Figure 2.50. Illustration of grain boundaries between individual crystalline domains.

grain boundary

grain boundary
crystallites (grains)

crystallites (grains)

crystallites (grains)

Figure 2.51. Schematic of a polycrystalline solid, with grain boundaries formed from dangling bonds
between neighboring metal atoms.

unsaturated (Figure 2.51). Hence, surfaces and interfaces are very reactive, often
resulting in the concentration of impurities in these regions.
A special type of grain boundary, known as crystal twinning, occurs when two
crystals of the same type intergrow, so that only a slight misorientation exists
between them. Twinned crystals may form by inducing alterations in the lattice