Measurements of propagation velocity of ultrasonic wave at a frequency of 10 mhz in pure and deuterated KDP single crystals*

The results of determination of all elastic constants of a KH2PO4 single crystal (KDP), and in the case of KD2xH2(1_x)PO4 crystals (DKDP) of constants C66 i C11 and the temperature dependence of the constant C66 at a frequency of 10 MHz are reported.
The measurements showed an effect of d.euteration on the constant 0 and on the change of the temperature dependence of C66 in the phase transition region.