Question

An example of anti-ferroelectric substance is (a) \(\mathrm{Fe}_{3} \mathrm{O}_{4}\) (b) \(\mathrm{PbZrO}_{3}\) (c) \(\mathrm{KH}_{2} \mathrm{PO}_{4}\) (d) \(\mathrm{BaTiO}_{3}\)

Short answer

The anti-ferroelectric substance is (b) bZrO3.

Step-by-step solution

Understand the concept of anti-ferroelectricity

Anti-ferroelectric materials have a crystal structure where adjacent dipoles are aligned in opposite directions, canceling out their net polarization. This structural characteristic differentiates them from ferroelectric materials, where dipoles align in the same direction.

Identify the correct anti-ferroelectric material

Among the options given, (a) e3O4 is a magnetic material, (c) KH2PO4 and (d) BaTiO3 are known ferroelectrics. The only material that fits the description of an anti-ferroelectric substance is (b) PbZrO3.

Key concepts

Crystal Structures

Crystal structures form the blueprint of materials and determine many of their properties. They are essentially an ordered arrangement of atoms, ions, or molecules in a repeated pattern extending throughout the material. In anti-ferroelectric materials, this ordered arrangement is crucial for their unique properties.

Anti-ferroelectric substances typically have complex crystal structures that facilitate the alignment of their dipoles in opposite directions. This unique layout ensures that the individual electric dipoles cancel each other out, leading to a net zero polarization. In contrast, ferroelectric materials have crystal structures that allow for dipole alignment in the same direction, resulting in a net polarization.

When studying materials like ext{PbZrO}_3, known for its anti-ferroelectric properties, one notices that its crystal structure is pivotal to its behavior. These structures make it possible for dipoles within the material to align oppositely, which is the primary character of anti-ferroelectricity.

Dipoles

Understanding dipoles is essential when exploring anti-ferroelectric materials. A dipole in this context refers to a pair of equal and oppositely charged or magnetized poles separated by a distance within the material.

In anti-ferroelectric materials, dipoles are aligned in such a way that adjacent dipoles point in opposite directions. This configuration is dictated by the material's crystal structure and dictates its macroscopic properties.

• The dipole alignment is meticulous, ensuring that their effects cancel each other out.
• This cancellation is what distinguishes anti-ferroelectric materials from ferroelectric ones, where dipoles tend to align in the same direction.

For instance, in ext{PbZrO}_3, this opposite alignment of dipoles across planes or layers is a prominent feature contributing to its classification as an anti-ferroelectric material.

Polarization Cancellation

One of the signature characteristics of anti-ferroelectric materials is polarization cancellation. In simple terms, polarization refers to the creation of a permanent dipole moment in a material when an electric field is applied.

For anti-ferroelectric materials, the intrinsic nature of their dipole arrangement leads to no net polarization, even in the presence of an electric field. Here's how it works:

• Adjacent dipoles are aligned oppositely within the crystal structure.
• This opposite alignment ensures that any individual dipole's effect is neutralized by its neighbor.
• As each dipole cancels out the other, the material exhibits no macroscopic polarization.

This characteristic polarization cancellation is central to differentiating anti-ferroelectric materials from other types, such as ferroelectrics where dipoles align in unison, leading to overall polarization. Hence, anti-ferroelectric substances like ext{PbZrO}_3 showcase this fundamental property remarkably.