Problem 46 - A Complete Resource Book in Chemistry for JEE Main

Question

An example of ferroelectric substance is (a) Tourmaline (b) Quartz (c) Barium titanate (d) Lead zirconate

Step-by-Step Solution

Answer

The ferroelectric substance is (c) Barium titanate.

Step 1: Understanding Ferroelectric Substances

Ferroelectric substances are materials that exhibit spontaneous electric polarization that can be reversed by the application of an external electric field. This property is similar to what happens in ferromagnetic materials, but with electric dipoles instead of magnetic ones.

Step 2: Evaluate the Options

We need to evaluate the given options against the properties of ferroelectric substances. Tourmaline and quartz are known for their piezoelectric properties, not ferroelectric. Barium titanate is renowned for its ferroelectric properties, while lead zirconate is a component in some ferroelectric ceramics.

Step 3: Select the Ferroelectric Substance

From the evaluation, barium titanate is a classic example of a ferroelectric material. It exhibits spontaneous electric polarization and the polarization direction can be reversed by applying an external electric field. Lead zirconate is also involved in some ferroelectric ceramics but is not typically used in its pure form as a ferroelectric.

Key Concepts

Barium Titanate

Barium Titanate, often abbreviated as BaTiO extsubscript{3}, is a well-known ferroelectric material. Its structure is what gives it these properties.

• In its crystal form, barium titanate has a perovskite structure, which is crucial for its ability to become polarized.
• The atoms within the crystal can shift slightly, causing a change in the electric dipole moment — this shift is what creates electric polarization.

Barium titanate is widely used in various applications due to its ability to change its electric dipole moment.
One common use is in capacitors, which are electronic components capable of storing and releasing electric energy.
When used in these devices, its ferroelectric properties help to achieve higher efficiency and performance.

Electric Polarization

Electric polarization refers to the alignment of electric dipoles in a material.

• In ferroelectric materials like barium titanate, this polarization is spontaneous. This means it occurs naturally without the need for an external force initially.
• However, what makes ferroelectric materials special is the reversible nature of this polarization when an external electric field is applied.

The concept of electric dipoles is central to understanding polarization.
Think of dipoles as tiny electric charges separated by a small distance — kind of like a tiny magnet but with positive and negative charges.
In ferroelectric substances, these dipoles can align themselves in a particular direction, leading to overall electric polarization of the material.

External Electric Field

An external electric field plays a key role in manipulating the electric polarization of ferroelectric substances.

• When applied to a ferroelectric material, this field can change the direction of the electric dipoles.
• This reversibility allows the material to have distinct states of polarization, which is crucial for its function in memory devices and capacitors.

Think of applying an external electric field as giving a gentle push to the electric dipoles, causing them to orient in a specific direction.
This push, coupled with the tendency for dipoles to return to their original position when the field is removed, makes ferroelectric materials useful in various technologies.
The ability to switch polarization states is what allows these materials to store information effectively, an essential feature in many modern electronic applications.