Growth and characterization of needle-like β-CaCr2O4 crystals

A mass of residue including needle-like β-CaCr2O4 crystals was obtained by heating a powder mixture consisting of CaCO3 and Cr2O3 on graphite powder in an alumina crucible with holes. The needle-like β-CaCr2O4 crystals were separated from the mass by hydrochloric acid. Yield of the crystals increased with increasing temperature above 1500 °C and reached about 41 wt% when heated at 1700 °C for 4 h. Then the average length and diameter of the crystals were 2.5 mm and 118 μm, respectively; the largest crystal was 3.8 mm in length and 187 μm in diameter. Needle axis of the crystals was the c axis.