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

deviation of the piezoelectric constant for graded KNN-based ceramics remains below 3.5% at 140 °C. Ultrasonic transducers capable of operating across a wide temperature range were designed and fabricated by using these graded KNN ceramics. The transducers demonstrated robust thermal stability and high-resolution imaging performance within a temperature range of 30 to 120 °C. C-scan images obtained across this temperature spectrum further illustrated their potential for NDT applications in diverse thermal environments. This study marks a significant breakthrough in the field of wide-temperature KNN-based ultrasonic transducers, as it indicates the first successful demonstration of imaging capabilities at temperatures exceeding 100 °C.