Molten salt synthesis of δ-CaCr2O4 and its annealing to prepare β-CaCr2O4

Molten salt synthesis (MSS), due to the high reactivity of salts, small diffusion distance and high mobility of species in molten salt, can not only reduce the synthesis temperature but also shorten the reaction time. Herein, MSS method was employed to synthesize δ-CaCr2O4 powder by using CaO, Cr2O3 as raw materials and CaCl2 which has a high solubility of CaO as molten salt. The influence of reaction time was investigated and δ-CaCr2O4 with platelet morphology was obtained after reaction for 2 h at 900 °C. Pure rod-like β-CaCr2O4 was further prepared by simply annealing the as-synthesized δ-CaCr2O4 in argon atmosphere for 3 h at 1100 °C. The magnetization and its corresponding reciprocal susceptibility of δ-CaCr2O4 and β-CaCr2O4 samples was also measured and calculated, which indicated a paramagnetic arrangement and an antiferromagnetic arrangement during the test temperature range 2-250 K, respectively.