- The primary reason ceramics exhibit a brittle nature is due to their high compressive strength but low tensile strength.
- Ceramics are composed of ionic and covalent bonds, which are strong but directional and rigid, limiting the ability of atoms to slip past each other under stress.
- This results in ceramics being very strong when subjected to compression, but very weak and prone to fracture when subjected to tension or bending forces.

- In addition, ceramics have limited plastic deformation because their atomic structure does not allow for the movement of dislocations as seen in metals.
- Therefore, instead of bending or deforming, ceramics tend to crack or break suddenly when the tensile stress exceeds their very low tensile strength.

In summary, the combination of strong but brittle bonding, high compressive strength, and low tensile strength is what primarily contributes to the brittle behavior of ceramics.

Reference: Materials Science and Engineering: An Introduction, 10th Edition, Chapter 5 - Mechanical Properties of Ceramics