Evaluation of polarization of embedded piezoelectrics by the thermal wave method

Abstract

This work demonstrates the benefit of the thermal wave method for the evaluation of the polarization state of embedded piezoelectrics. Two types of samples were investigated: A low-temperature co-fired ceramics (LTCC)/lead zirconate titanate (PZT) sensor-actuator and a macro-fiber composite (MFC) actuator. At modulation frequencies below 10 Hz, the pyroelectric response was governed by thermal losses to the embedding layers. Here, the sample behavior was described by a harmonically heated piezoelectric plate exhibiting heat losses to the environment characterized by a single thermal relaxation time.

Polarization characterization of PZT disks and of embedded PZT plates by thermal wave methods

“…There is only a small difference to the Cole-Davidson-model in [2] characterizing a relaxation time distribution with β = 0.83. The thermal relaxation time amounts to 0.16 s resulting in a thermal conductance at the PZT/LTCC interface of 3083 W/m²K which is almost the same value as reported in [1]. The imaginary part is additionally shifted down by approximately 0.1 nA.…”

“…Measurement results for the LTCC/PZT sensor-actuator and the MFC actuator using AC coupling with a cut-off frequency of 1 Hz have been previously described in [1]. In this case, signals at lower frequencies were suppressed and the phase was changed.…”

“…Thermal wave methods (TWMs) are a suitable approach for the non-destructive evaluation of the polarization state of piezoelectrics [1,2]. TWMs enable the determination of the pyroelectric coefficient depth profile from the time or frequency dependence of the pyroelectric current.…”

Characterisation of the polarisation state of embedded piezoelectric transducers by thermal waves and thermal pulses

“…In the case of LIMM, we consider a harmonically heated piezoelectric plate exhibiting heat losses to the environment, characterised by a thermal relaxation time τ th (Suchaneck et al, 2012). The steady-state periodic solution of this problem in the form of an infinite series is given by Bauer and Ploss (1990) and Carslaw and Jaeger (1959):…”

Evaluation of polarisation state of light metal embedded piezoelectrics

“…1 To ensure the functionality of the integrated piezoelectric modules after the fabrication process, the polarisation state is determined non-destructively by thermal wave methods. 2 The devices are irradiated by a modulated laser beam, and the time or frequency dependences of the pyroelectric current are recorded, which provide insight into the polarisation distribution.…”