Characteristics of Acoustic Emission Sensor Using Lead-Free (LiNaK)(NaTaSb)O3 Ceramics for Fluid Leak Detection at Power Plant Valves

In this study, acoustic emission (AE) sensor was fabricated using lead-free (LiNaK)-(NbTaSb)O3 ceramics for preventing environmental pollution. The structure of the AE sensor was designed as a Langevin-type one with air backing. The electromechanical coupling factor kp and piezoelectric constants d33 and g33 of lead-free (LiNaK)-(NbTaSb)O3 ceramics were 0.49, 300 pC/N, 27.02 mV·m/N, respectively. The peak sensitivity and frequency of the AE sensor using this ceramic material were 66.3 dB and 29.4 kHz, respectively. The results for fluid leak detection at a power plant valve were as follows; the peak frequency of response was 25 kHz at 2 and 6 kgf/cm2 N2 gas pressures, and increased up to 50 kHz at a 10 kgf/cm2 N2 gas pressure. The magnitude of the response voltage was about 40 mV at all the pressures.