Growth of CuFeO$_2$ Single Crystals by the Optical Floating-Zone Technique

TL;DR

This paper reports the successful growth of large CuFeO₂ single crystals using the optical floating-zone method, detailing the growth conditions, challenges due to incongruent melting, and characterization techniques.

Contribution

It introduces a method for growing large, high-quality CuFeO₂ single crystals suitable for substrate applications, addressing melting behavior complexities.

Findings

Crystals up to 50 mm long and 10 mm diameter were grown.

Stable growth requires low rates and lamp power adjustments.

Crystals characterized by X-ray diffraction and fluorescence.

Abstract

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.