Dielectric measurements in highly deuterated betaine phosphite

We have performed a detailed investigation of the dielectric properties of deuterated betaine phosphite (D-BPI) using broadband dielectric spectroscopy, measurements of the non-linear susceptibility, of the pyroelectric coefficient, and of the field dependent polarization. D-BPI becomes ferroelectric in two successive phase transitions at Tc2 = 272 K and Tc3 = 266 K. At frequencies v > 100 MHz a critical slowing down of the order dynamics at 266 K could be observed. In addition, we found evidence for a third polar phase transition at Tc4 = 250 K. At temperatures around 150 K a relaxational process, most probably due to domain wall motions, shows up which is highly field dependent with an energy barrier of 5300 K at low fields.

Keywords:

• pyroelectric coefficient
• dielectric spectroscopy
• hysteresis loops
• nonlinear susceptibiliity