Lead-free Piezoelectric KNN-based Pin Transducers for Structural Monitoring Applications

A 2.4 mm diameter piezoelectric ceramic disc was used to construct a spring-loaded pin-type transducer for intelligent monitoring of systems. Two types of lead-free KNN-based ceramics (0.95K0.5Na0.5 (Nb0.94Sb0.06)O 3 — 0.05LiTaO3 + 1.25 mol% BaO and K0.5Na 0.5NbO3 -0.75 mol% K5.4Cu1.3Ta 10O29) were selected as a sensing element of the pin. The piezoelectric spring-loaded pins were mounted on the corners of the aluminum plate for the performance evaluation using a laser ultrasonic technique. The signals detected by transducers with different sensing elements including lead-based ceramics have been compared. The capability of impact detection of the lead-free transducers was shown to be comparable to that of the lead-based one. It is envisaged that lead-free piezoelectrics will become the important transducer materials in the next generation nondestructive evaluation technology.

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