Crystal growth of iron-based superconductor FeSe0.94 by KCl flux method

•SC crystals of FeSe0.94 bigger than previous reports are grown by KCl flux method.•The crystal sizes are 6 × 3 × 0.1–0.2 mm3 or 5 × 5 × 0.1–0.2 mm3; the TC is around 10 K.•Relatively big crystal size is realized by optimizing crystal growth conditions.•Optimized are the dissolution and convection, temperature gradient and flux content.

Single crystals of iron-based superconductor FeSe0.94, the 11 phase, have been grown using KCl as flux. The size of as-grown crystals is up to 6 × 3 mm2 or 5 × 5 mm2. The relatively big crystal size is achieved by optimizing the experimental scheme. The main phase of the crystal samples is identified to be tetragonal β-FeSe by X-ray diffraction analysis. The superconducting transition temperature is determined to be around 10 K by both electron transport and diamagnetism measurements.