Nonlinear electromechanical behaviour of KDP near its phase transition

Potassium dihydrogen phosphate (KDP) undergoes a ferroelectric phase transition at 123 K. The linear elastic and electromechanical properties are well known. This paper deals with simultaneous measurements of the transit time and the attenuation variations of pulsed ultrasound in parallelepiped samples of KDP using a picosecond sampling oscilloscope. These variations are introduced by low frequency electric fields. The results can be used to determine complex nonlinear piezoelectric coefficients above and below the phase transition of KDP.