Elastic properties of KH2PO4 at the ferroelectric phase transition

• We report results of ultrasonic studies on a single crystal of KDP.
• The elastic moduli c11, c33, c44 and c66 were calculated from sound velocity data.
• The temperature dependences of moduli c11, c33, c44 and c66 were measured.
• The elastic constants c11 and c33 can be presented in a common reduced form.

We report results of ultrasonic studies of a single crystal of KDP in the temperature range 2–300 K. The longitudinal and transverse sound velocities along [001] and [100] directions were obtained as functions of temperature. The analysis of the temperature evolution of pseudomoduli c11 and c33 in the ferroelectric phase shows that these quantities can be approximated by the expression cii~(T−T0)0.5cii~(T−T0)0.5 in the temperature range 0.001K