  Surface acoustic wave (SAW) devices based on thin films of ZnO are a well
established technology. However, SAW devices on bulk ZnO crystals are not
practical at room temperature due to the significant damping caused by finite
electrical conductivity of the crystal. Here, by operating at low temperatures,
we demonstrate effective SAW devices on the (0001) surface of bulk ZnO
crystals, including a delay line operating at SAW wavelengths of {\lambda} = 4
and 6 {\mu}m and a one-port resonator at a wavelength of {\lambda} = 1.6
{\mu}m. We find that the SAW velocity is temperature dependent, reaching $v
\simeq 2.68$ km/s at 10mK. Our resonator reaches a maximum quality factor of
$Q_i \simeq 1.5\times 10^5$, demonstrating that bulk ZnO is highly viable for
low temperature SAW applications. The performance of the devices is strongly
correlated with the bulk conductivity, which quenches SAW transmission above
about 200 K.
