Comprehensive Performance Optimization in KNN-Based Piezoelectric Ceramics for an Ultrasonic Transducer

Area of Science:

• Materials Science
• Ceramic Engineering
• Solid State Physics

Background:

• Potassium sodium niobate (KNN) ceramics offer an eco-friendly alternative to lead-based piezoelectrics due to their high Curie temperature (T_C), good piezoelectric coefficients, and low density.
• A key challenge is optimizing piezoelectric properties (d₃₃, k_p) while maintaining thermal stability and T_C.

Purpose of the Study:

• To develop a targeted doping strategy for KNN ceramics to simultaneously enhance piezoelectric performance and thermal stability.
• To investigate the relationship between doping, microstructure, and piezoelectric properties in KNN-based materials.

Main Methods:

• Controlled acceptor doping was employed to regulate grain size and induce nanodomain formation in KNN ceramics.
• Microstructural characterization and piezoelectric property measurements were conducted on optimized KNN compositions.
• Fabrication and testing of an ultrasonic transducer using the optimized KNN material.

Main Results:

• The optimized KNN composition (x = 0.4) exhibited excellent densification and a uniform microstructure.
• Exceptional piezoelectric properties were achieved: d₃₃ = 358 pC/N and k_p = 56.6%.
• A high T_C of 315 °C and good thermal stability were demonstrated. The ultrasonic transducer showed a 3.19 MHz center frequency and 60% bandwidth, enabling high-resolution imaging.

Conclusions:

• Targeted doping is an effective strategy for optimizing KNN ceramics for enhanced piezoelectric performance and thermal stability.
• The optimized KNN material demonstrates superior signal transduction capabilities for mid-to-high frequency ultrasonic devices and energy harvesting.
• KNN ceramics represent a viable, high-performance, lead-free piezoelectric material for next-generation electronic applications.