Hydrothermal synthesis of delafossite CuFeO2 crystals at 100 °C

Abstract

In this work, we first report a fast, facile hydrothermal method to synthesize delafossite CuFeO₂ crystals through low-temperature (100–160 °C) reaction. In detail, CuFeO₂ crystals with submicron-sized (100–300 nm) could be obtained based on hydrothermal reaction from the starting materials of Cu(NO₃)₂, FeCl₂ and NaOH at 100 °C for 12 h. Furthermore, the TG curve of CuFeO₂ is similar to other copper based delafossite oxides, and CuFeO₂ tend to be oxidized by O₂ in air at a higher sintering temperature (>400 °C). The obtained CuFeO₂ film has an optical transmission of 50–60% in visible region, and the optical bandgap for the direct band transition was estimated to be 3.18 eV. Finally, the magnetic hysteresis loops measured at room temperature show CuFeO₂ crystals exhibit antiferromagnetic behavior, the Néel temperature (T_N) about 12 K and the biggest magnetic susceptibility around 0.168 emu g⁻¹. This quick and facile method maybe opens a new route for preparation of CuFeO₂ crystals, due to the low reaction temperature and short reaction time.