  CuFeO$_2$ single crystals up to 50 mm in length and up to 10 mm in diameter
were grown by the optical floating-zone method. Stoichiometric polycrystalline
rods with a diameter of 6-12 mm were used as feed materials to produce crystals
of sufficient size to be used as substrates for the growth of thin films of
delafossites. For stable growth along the $c$-axis, low growth rates of 0.4
mm/h are necessary. Due to the incongruent melting behavior of CuFeO$_2$, a
stable melt zone requires adjustment of the lamp power during growth. The
melting of CuFeO$_2$ is not simply incongruent because the thermodynamic
equilibrium includes more than two solid phases and the melt; the gas phase is
also involved. The crystals were characterized by X-ray diffraction and X-ray
fluorescence measurements.
