LAUSR

Abstract This paper investigates the reaction mechanism in mechanochemical synthesis of Cu 2-x Se by vibrational milling of (Cu+Se) powder mixture. The effects of milling time, milling mode, ball-to-powder weight ratio (BPWR), and Cu/Se molar ratio in the starting composition on the phase assemblage of the products are investigated. It is found that, the synthesis of Cu 2-x Se is improved by increasing milling time, BPWR, and Cu/Se ratio. For a fixed total milling time, continuous milling is better than intermittent milling to facilitate the formation of Cu 2-x Se. By continuous milling for 20 min with BPWR = 6 and Cu/Se = 2, almost single-phase β-Cu 2-x Se is produced except for minor un-reacted Cu. A diffusion-controlled reaction mechanism is proposed for the mechanochemical synthesis of Cu 2-x Se, where intermediate phases such as CuSe and Cu 3 Se 2 with lower Cu/Se ratios are produced at first and then gradually converted into Cu 2-x Se with the diffusion of Cu atoms.