Graded KNN-Based Lead-Free Ultrasonic Transducer for Wide-Temperature Nondestructive Testing Imaging

Area of Science:

• Materials Science
• Nondestructive Testing (NDT)
• Ultrasonics

Background:

• Development of lead-free piezoelectric materials is crucial for advanced NDT applications.
• Existing ultrasonic transducers face limitations in high-temperature environments.
• Potassium sodium niobate (KNN)-based ceramics offer potential for wide-temperature applications.

Purpose of the Study:

• To optimize materials and devices for wide-temperature, high-resolution NDT imaging.
• To develop and integrate graded lead-free KNN ceramics with wide-temperature ultrasonic transducers.
• To demonstrate the feasibility of NDT imaging at elevated temperatures exceeding 100°C.

Main Methods:

• Engineered graded KNN ceramics with multiple crystalline phases (O-T/R-O-T/R-T) for enhanced thermal stability and piezoelectric performance.
• Designed and fabricated ultrasonic transducers utilizing the optimized graded KNN ceramics.
• Evaluated transducer performance, including piezoelectric constant deviation and imaging capabilities, across a temperature range of 30°C to 120°C.

Main Results:

• Graded KNN ceramics exhibited minimal piezoelectric constant deviation (<3.5%) even at 140°C.
• Fabricated ultrasonic transducers demonstrated robust thermal stability and high-resolution imaging from 30°C to 120°C.
• Successful C-scan imaging was achieved across the tested temperature spectrum, validating NDT potential in diverse thermal conditions.

Conclusions:

• This study presents the first successful demonstration of wide-temperature KNN-based ultrasonic transducer imaging capabilities above 100°C.
• The integrated approach of graded KNN ceramics and specialized transducers overcomes previous temperature limitations in NDT.
• These findings represent a significant advancement for NDT applications in high-temperature industrial and operational environments.