Method for preparing a P-type ZrCoSb-based half-Heusler single crystal alloy with a chemical composition of ZrCoSb1-xSnx by vertical bridgman directional crystallization

A method for preparing a P-type ZrCoSb-based half-Heusler single crystal alloy, comprising:

• subjecting alloy raw materials to smelting under a first protective atmosphere to obtain a half-Heusler polycrystalline alloy ingot, the alloy raw materials corresponding to a chemical composition of the P-type ZrCoSb-based half-Heusler single crystal alloy;
• and
• subjecting the half-Heusler polycrystalline alloy ingot to vertical Bridgman directional crystallization under a second protective atmosphere to obtain the P-type ZrCoSb-based half-Heusler single crystal alloy;
• wherein
• the P-type ZrCoSb-based half-Heusler single crystal alloy has a chemical composition of ZrCoSb1-xSnx, x in the ZrCoSb1-xSnx being in a range of 0.20≤x≤0.3;
• the P-type ZrCoSb-based half-Heusler single crystal alloy has an MgAgAs-type crystal structure;
• the vertical Bridgman directional crystallization is conducted at a pressure of 112,000 Pa to 130,000 Pa;
• and
• the vertical Bridgman directional crystallization is performed by a process consisting of:
• placing the half-Heusler polycrystalline alloy ingot into a crucible;
• melting the half-Heusler polycrystalline alloy ingot by heating to a material melting temperature under the second protective atmosphere, to obtain a molten alloy material in the crucible;
• and
• subjecting the molten alloy material to directional crystallization by taking the crucible as a reference and raising a heating furnace cavity along the crucible, wherein
• raising the heating furnace cavity along the crucible is conducted at a rate of 0.3 mm/h to 2 mm/h;
• and
• heating to the material melting temperature is performed by:
• heating to a first temperature at a first heating rate;
• and
• heating to the material melting temperature at a second heating rate;
• wherein the first heating rate is in a range of 10° C./min to 15° C./min, and the first temperature is 1,000° C.;
• and
• the second heating rate is in a range of 2° C./min to 5° C./min, and the material melting temperature is in a range of 1,560° C. to 1,600° C.