Which material is not typically used as the active piezoelectric element in modern transducers?

• A. Piezo-electric crystal
• B. Quartz
• C. Less zirconate
• D. Barium titinate

Answer: (B)

The main idea is that modern ultrasound transducers rely on piezoelectric materials with very high electromechanical coupling and easy manufacturability into thin, dense elements for array construction. Lead zirconate titanate (PZT) ceramics are the workhorse because they offer strong conversion between electrical energy and mechanical vibrations, and they can be fabricated into the small, uniform elements needed for high-frequency arrays. Barium titanate-based ceramics are also used in some transducers, though less common than PZT, but they still fit the ceramic active-element approach.

Quartz, while a piezoelectric crystal, does not fit well here. Its coupling is much lower, so for the same drive voltage it generates less ultrasonic energy. It is also harder to shape into the thin, densely packed, reproducible elements required for modern transducer arrays, making it inefficient and less cost-effective for broad medical ultrasound use. Therefore, quartz is not typically used as the active piezoelectric element in modern transducers.