Question

Which of the following is not a ferroelectric compound ?

• A. Rochelle salt
• B. $K_4\left[Fe\right(CN{)}_6]$
• C. $BaTi{O}_3$
• D. $K{H}_{2}P{O}_4$

Answer 1

Answer: (B)

$K_4\left[Fe\right(CN{)}_6]$

Ferroelectricity is a spontaneous electric polarization of a material that can be reversed by the application of an external electric field. The term is used in analogy to ferromagnetism in which a material exhibits a permanent magnetic moment. Ferromagnetism was already known when ferroelectricity was discovered in $1920$ in Rochelle salt by Valasek. Thus, the prefix ferro meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not have iron in their lattice.
Example are barium titanate ($BaTi{O}_3$) and Rochelle salt.