Acoustic velocity, acoustic absorption coefficient, and acousto‐optical figure of merit for longitudinal acoustic modes of this crystal have been measured at room temperature. Among some interesting combinations of acoustic and optical modes, the longitudinal wave propagated parallel to the principal axisXof the index ellipsoid which lies in the (010) plane with the light polarized parallel to theYaxis (two‐fold axis,b) has been found to be particularly useful for acousto‐optical device applications because of its high figures of meritM(=n6p2/ &rgr;v3) = 127×10−18sec3/g andM′(=n7p2/ &rgr;v) = 242×10−7cm2sec/g and relatively low acoustic loss, 4.2 dB/cm at 300 MHz.