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Chapter 19: Problem 16

Briefly explain why the thermal conductivities are higher for crystalline than for noncrystalline ceramics.

Short Answer

Expert verified
Crystalline ceramics have higher thermal conductivities than noncrystalline ceramics due to their well-ordered atomic structure and fewer defects. The increased heat transport within the material is attributed to the periodic structure of the crystal lattice, which allows phonons (primary heat carriers in ceramics) to travel more freely and effectively within the material. In contrast, noncrystalline ceramics have a more disordered and random atomic arrangement, leading to a higher number of defects and grain boundaries that scatter phonons, resulting in lower thermal conductivity.

Step by step solution

01

Understand the difference between crystalline and noncrystalline ceramics

Crystalline ceramics have a well-ordered and repeating atomic structure, while noncrystalline ceramics have a more disordered and random atomic arrangement. Because of this difference in atomic structure, their thermal conductivities are affected.
02

Discuss the factors affecting thermal conductivity in ceramics

Thermal conductivity in a material is the ability to transfer heat through it. It is mainly influenced by the number of available heat carriers (electrons in metals, phonons in ceramics), the mobility of these carriers, and the presence of any defects or grain boundaries that can scatter them.
03

Explain how the structure of crystalline ceramics contributes to higher thermal conductivity

In crystalline ceramics, the regular and ordered arrangement of atoms allows for effective heat transport via phonons. The periodic structure of the crystal lattice results in a lower number of defects and grain boundaries that can scatter phonons. This means that phonons can travel more freely within the material, leading to higher thermal conductivity.
04

Explain how the structure of noncrystalline (amorphous) ceramics contributes to lower thermal conductivity

In noncrystalline ceramics, the disordered and random atomic arrangement leads to a higher amount of defects, dislocations, and grain boundaries. These structural irregularities increase the scattering of phonons, reducing their mobility within the material. This decrease in phonon mobility results in lower thermal conductivity. In conclusion, crystalline ceramics have higher thermal conductivities than noncrystalline ceramics due to their well-ordered atomic structure and fewer defects, which allows for more efficient heat transport via phonons.

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Most popular questions from this chapter

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