Determination of the piezoelectric coefficient in lead-free ceramics via Fizeau fiber optic interferometry

This study presents an interferometric methodology to determine the dynamic piezoelectric coefficient ($d_{33}^{*}$) of lead-free piezoelectric ceramics. Using a fiber optic Fizeau interferometer, we analyze the (K₀.₄₄Na₀.₅₂Li₀.₀₄)(Nb₀.₈₆Ta₀.₁₀Sb₀.₀₄)O₃ (KNL-NTS) composition, an eco-friendly alternative to traditional lead-based materials. The displacement of the ceramic samples under a varying electric field was measured, allowing the dynamic strain-time curve to be obtained and analyzed. This temporal displacement analysis reveals the material's real-time electromechanical response, providing insights into its behavior under dynamic excitation. The interferometric method demonstrates advantages such as non-invasive measurement, self-calibration, and accurate determination of $d_{33}^{*}$. The dynamic piezoelectric coefficient was measured to be around 840 pm/V, with results validated using the resonance frequency method.