Metallic and Ceramic Structure
Metallic and Ceramic Structure
Metallic and Ceramic Structure
POLYMORPHISM
The substance existing more then one crystalline form is called
polymorphous substance and the phenomena as polymorphism.
e.g.Nacl is found in cubic and octahedral.
Allotropy
It is the ability of substance to exist in more then one form in the same
crystalline state.
e.G pure iron has a BCC crystal structure at room temperature, which
changes to FCC iron at 912 celcius.
3.7 CRYSTAL SYSTEMS
Lattice parameters
The unit cell geometry is completely defined in terms of six parameters: the
three edge lengths a,b,and c,and the three interaxial angles are
These are indicated in Figure 3.4, and are sometimes termed the lattice
parameters.
Crystallographic Points, Directions,
and Planes
3.8 POINT COORDINATES
The position of any point located within a unit cell may be specified in
terms of its coordinates as fractional multiples of the unit cell edge
lengths (i.e., in terms of a, b,and c).
𝑛𝜆 = 𝑆𝑄 + 𝑄𝑇
𝑆𝑄=𝑑ℎ𝑘𝑙 sin 𝜃
𝑄𝑇=𝑑ℎ𝑘𝑙 sin 𝜃
𝑛𝜆 = 𝑑ℎ𝑘𝑙 sin 𝜃 + 𝑑ℎ𝑘𝑙 sin 𝜃
n𝜆 = 2𝑑ℎ𝑘𝑙 sin 𝜃
Diffraction technique
• The diffractometer is an apparatus used to
determine the angles at which diffraction
occurs for powdered specimens.
3.17 NONCRYSTALLINE SOLID
• Noncrystalline solids lack a systematic and regular
arrangement of atoms over relatively large atomic
distances.
• Sometimes such materials are also called amorphous
(meaning literally without form), or supercooled
liquids.Their atomic structure resembles that of a liquid.
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