Ferroelectricity — Rochelle salt classification State whether the following statement is true or false: “Rochelle salt (sodium potassium tartrate) is a ferroelectric material.”

Introduction / Context:
Ferroelectrics exhibit a spontaneous electric polarization that can be reversed by an external electric field and typically show Curie transitions separating ferroelectric and paraelectric phases. Rochelle salt is historically significant as one of the first discovered ferroelectrics.

Given Data / Assumptions:

• Material: Rochelle salt (sodium potassium tartrate tetrahydrate).
• Standard definition of ferroelectricity (switchable spontaneous polarization).

Concept / Approach:
Rochelle salt possesses a spontaneous polarization in certain temperature ranges and exhibits a hysteresis loop in the polarization–electric field characteristic, satisfying the criteria for ferroelectricity. Therefore, the statement is true in the usual materials science sense.

Step-by-Step Solution:
Recall ferroelectric definition: switchable spontaneous polarization.Note Rochelle salt’s classic ferroelectric behavior and historical demonstrations.Conclude the statement is true.

Verification / Alternative check:
Phase diagrams for Rochelle salt show ferroelectric phases between two Curie temperatures, consistent with its classification.

Why Other Options Are Wrong:
“False” or “piezoelectric only” overlook its ferroelectric switching; while many ferroelectrics are also piezoelectric, ferroelectricity is the stronger criterion here.

Common Pitfalls:

• Assuming all piezoelectrics are ferroelectric (not true), or vice versa (often but not always true).
• Ignoring temperature-dependent phase behavior; though nuanced, the material is indeed ferroelectric.

Final Answer:
True