Thermoelectrical Characterization of Piezoelectric Diaphragms: Towards a Better Understanding of Ferroelectrics for Future Memory Applications

This work deals with the thermoelectric characterization of commercial lead zirconate titanate (PZT) based piezoelectric diaphragms. An in-depth analysis of the piezo- and ferroelectric behavior of the samples was carried out by measuring current voltage curves and polarization hysteresis cycles in a wide temperature range. We demonstrate that, as the temperature decreases, higher electric fields are needed to completely polarize the sample. Furthermore, I-V measurements, polarization hysteresis loops and coercive fields allow us to confirm that the samples present different grain sizes. From impedance measurements, resonance frequency values, capacitance and permittivity were determined at temperatures ranging from 100 to 320 K. It is shown that impedance maxima shift towards greater frequency values when decreasing the temperature, which is mainly attributed to the appearance of an internal stress that generates larger stiffness in the ceramic. Finally, an electroacoustic characterization was made by measuring the sound pressure of the diaphragms in the human hearing frequency range.