Phase velocities of ultrasound waves and elastic modules in the IIb type synthetic diamond single crystal

First the results of experimental studies on the propagation of bulk acoustic waves ($30$–$120$ MHz) in the IIb type synthetic diamond single crystal have been presented in comparison with the appropriate data in the IIa type synthetic diamond. Data obtained were used to calculate all the elastic moduli of IIb type diamond (in GPa) as $C_{11}=1080.0$, $C_{12}=149.0$, and $C_{44}=577.4$. Parameter of elastic anisotropy $A$ in the IIb type diamond exceeds by $2.5\%$ an appropriate value in the IIa type diamond.