The Curie Temperature has which effect on the piezoelectric material in ultrasound transducers?

• A. the backing material delaminates from the active element
• B. the glue binding the crystal & matching layer melts
• C. the ferroelectric material is depolarized
• D. the matching layer changes its impedance

Answer: (C)

The Curie temperature is the point at which a ferroelectric piezoelectric material loses its spontaneous polarization and becomes paraelectric. In ultrasound transducers, the piezoelectric effect depends on that polarization to convert electrical energy into mechanical vibration and back. When temperature rises above the Curie point, the material’s remnant polarization vanishes, domain orientation becomes random, and the piezoelectric coefficients drop toward zero. The crystal becomes depolarized, so the transducer loses its piezoelectric response and performance degrades. The other scenarios—delamination of the backing, melting glue, or impedance changes in the matching layer—are mechanical or material-property effects of heat, not depolarization of the ferroelectric material.