Explain piezoelectricity and the reason why it manifests onl

)Explain piezoelectricity and the reason why it manifests only in some materials with specific characteristics.

Solution

Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress. When piezoelectric material is placed under mechanical stress, a shifting of the positive and negative charge centers in the material takes place, which then results in an external electrical field.

In most crystals (such as metals), the unit cell (the basic repeating unit) is symmetrical; while in piezoelectric crystals, unit cell isn\'t symmetrical. Normally, piezoelectric crystals are electrically neutral: the atoms inside them may not be symmetrically arranged, but their electrical charges are perfectly balanced: a positive charge in one place cancels out a negative charge nearby. However, if you squeeze or stretch a piezoelectric crystal, you deform the structure, pushing some of the atoms closer together or further apart, upsetting the balance of positive and negative, and causing net electrical charges to appear. This effect carries through the whole structure so net positive and negative charges appear on opposite, outer faces of the crystal.