Characterization of ferroelectrics by thermal wave methods

In this work, pyroelectric spatial profiles of SBN crystals, BaTi1−xSnxO3 ceramics, and Pb(Zr,Ti)O3 thin films were determined from the pyroelectric current spectrum caused by the interaction of thermal waves with the internal electric field and the unknown polarization distribution. For sinusoidal modulation, the pyroelectric current frequency dependence up to 10 MHz and phase shift between pyroelectric current and heat flux were analyzed to reconstruct the polarization distribution by solution of the Fredholm integral equation and by a Tikhonov regularization method for stable MATLAB numerical solutions. For the dynamic method with rectangular modulation, an approximate pyroelectric response in dependence on penetration depth was calculated. In this case, low modulation frequencies are required for the investigation of deep regions. Digital methods of signal processing were used to enable experiments below 1 Hz.