Improved preparation method of nano composite thermoelectric material

The invention discloses an improved preparation method of a nano composite thermoelectric material in the technical field of preparation of nano thermoelectric materials. The improved preparation method comprises the following steps: smelting Cu, Se and La block raw materials into cast ingots by adopting induction smelting equipment; the S powder weighed according to the chemical formula ratio and the crushed cast ingot thermoelectric material are put into a ball milling device together, and the ball milling device is used for grinding the S powder and the cast ingot thermoelectric material; in the grinding process, the ball-milling device can fully grind the unqualified cast ingots and powder, and the qualified powder can be fed into a graphite mold by the ball-milling device; placing the graphite mold loaded with the primary ball-milled powder in a spark plasma sintering cavity, and sintering the graphite mold into a block in a vacuum atmosphere; crushing the sintered blocks, and carrying out secondary ball