A testbed for high voltage, high bandwidth characterization of nonlinear dielectrics

Summary form only given. Ferroelectric materials exhibit a hysteretic response similar to the B-H curve of magnetic materials. With ferroelectric materials the polarization-electric field (P-E) hysteretic loop is typically measured at low frequencies. However, the material behavior at high frequencies is less understood. To address this information gap, a test bed has been created to characterize non-linear material behavior at high frequencies and high voltages. This paper will report testbed goals in addition to design, assembly, analysis and issues. Preliminary results will also be presented from testing commercially available ferroelectric capacitors and materials, including 10 nf non-linear BaTiO-based capacitors and 3 mm thick lead zirconate titanate (PZT)-based materials. The main goal of the test bed is to drive a 1-50 nF ferroelectric sample around its polarization-electric field (P-E) loop with a low inductance circuit (10 nH) and high bandwidth (1 GHz) diagnostics at voltages up to 20 kV and currents up to 10 kA. A secondary goal is to drive the sample through P-E sub-loops to measure the sample response at high frequencies within the P-E loop. Polarization of the sample is obtained by integrating the current passing through the sample and dividing by its cross-sectional area. The electric field is determined by measuring the voltage across the sample and dividing by its thickness. Simulation of the circuit and analysis of the data require modeling of the sample behavior internal to the P-E loop and along its boundaries. A hyperbolic tangent (Fermi function) model that depends on the initial values of P and E and the polarity of the current provides a reasonable model for low bandwidth measurements of most materials. However P-E loops with sharper corners and/or a strong variation with frequency may require a model with a higher order exponential dependence, and a free parameter to characterize the sharpness of the corners independent of the slope of the loop through zero polarization. Simulation and analysis of our preliminary results will be discussed.