Structural changes of MoS₂ nano-powder in dependence on the annealing temperature

Abstract

To search for structural changes of molybdenum disulphide (MoS₂) nano-powder under thermal treatment, the annealing of the powder was carried out in vacuum or in argon. MoS₂ powder with a grain size of 3–5 nm was synthesized by a chemical method. The temperature of annealing was varied in the range of 380–1000 °C. The time of annealing was varied in the range from 4 h (380 °C) to 5 min (1000 °C). X-ray diffraction and transmission electron microscopy analyses were made to see the character of the change of the crystallization process and the curvature of (002) MoS₂ planes. The increase of crystalline phase and the decrease of amorphous phase in the powder appears as a result of the rise of the annealing temperature. The sample annealed at T_ann=380 °C and 500 °C has a small curvature of (002) planes and more enlarged grains in comparison with non-annealed MoS₂ powder. The increase of the annealing temperature to T_ann=700 °C leads to a strong curvature of the (002) planes. The character of the curved planes varies from quite long planes with a large radius of curvature to right-angle-form and U-form structures. The increase of the annealing temperature to T_ann=1000 °C leads to a strong crystallization of the powder and a reduction of the amorphous phase.