Growth of CuFeO\(_2\) Single Crystals by the Optical Floating-Zone Technique

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.