Material comprising a semi-heusler alloy and process for producing such a material

Abstract

A material includes at least two different alloy phases. At least two alloy phases are each formed by at least one thermodynamically stable semi-Heusler alloy. The semi-Heusler alloys of the at least two alloy phases are different from one another. At least two of the semi-Heusler alloys have at least partly sintered particles that have an average particle size D 50 in the range of less than or equal to 100 nm. Such a material has particularly good thermoelectric properties. A process is implemented to produce the material.

What is claimed is: 
     
         1 . A material, comprising:
 at least two different phases, at least two phases each being formed by at least one thermodynamically stable semi-Heusler alloy, the semi-Heusler alloys of the at least two phases being different from one another and at least two semi-Heusler alloys having at least partly sintered particles that have an average particle size D 50  in the range of less than or equal to 100 nm.   
     
     
         2 . The material according to  claim 1 , wherein at least one semi-Heusler alloy has particles having an average particle size D 50  in the range from less than or equal to 30 nm. 
     
     
         3 . The material according to  claim 1 , wherein the particles have an at least bimodal particle size distribution. 
     
     
         4 . The material according to  claim 1 , further comprising two thermodynamically stable phases whose semi-Heusler alloys are present in a ratio of from 1:5 to 5:1. 
     
     
         5 . The material according to  claim 1 , wherein the phases are thermodynamically stable up to a temperature of greater than or equal to 950° C. 
     
     
         6 . The material according to  claim 1 , wherein at least two semi-Heusler alloys are each based on an alloy selected from the group consisting of Ti 0.68 Zr 0.18 Hf 0.14 NiSn, Ti 0.43 Zr 0.28 Hf 0.29 NiSn, Ti 0.21 Zr 0.4 Hf 0.39 NiSn, Ti 0.24 Hf 0.76 NiSn, Ti 0.61 Hf 0.39 NiSn, Ti 0.83 Hf 0.17 NiSn, Ti 0.83 Zr 0.17 NiSn, Ti 0.65 Zr 0.35 NiSn, Ti 0.31 Zr 0.69 NiSn, Zr 0.78 Hf 0.22 NiSn, Zr 0.55 Hf 0.45 NiSn, Zr 0.37 Hf 0.63 NiSn, TiNiSn, ZrNiSn, HfNiSn. 
     
     
         7 . The material according to  claim 1 , wherein the at least two semi-Heusler alloys are based on the empirical formula Ti x Zr y Hf z NiSn, where at least one metal from the group consisting of titanium, zirconium and hafnium is at least partly replaced by a metal from the group consisting of scandium, yttrium, niobium, vanadium, manganese, aluminum, silver. 
     
     
         8 . The material according to  claim 1 , wherein the at least two semi-Heusler alloys are based on the empirical formula Ti x Zr y Hf z NiSn, where nickel is at least partly replaced by a metal from the group consisting of manganese, iron, cobalt, copper, zinc and silver. 
     
     
         9 . The material according to  claim 1 , wherein the at least two semi-Heusler alloys are based on the empirical formula Ti x Zr y Hf z NiSn, where tin is at least partly replaced by a metal from the group consisting of antimony, tellurium, bismuth, indium, gallium, aluminum. 
     
     
         10 . A process for producing a material having two different phases, comprising:
 forming particles of at least one alloy body having at least two different thermodynamically stable semi-Heusler alloys, the particles having an average particle size D 50  in the range of less than or equal to 100 nm;   mixing the particles in a predetermined ratio; and   sintering the mixture.   
     
     
         11 . The process according to  claim 10 , wherein at least one thermodynamically stable semi-Heusler alloy is provided by:
 producing a metal mixture comprising nickel, tin and at least one of titanium, zirconium and hafnium in a predetermined weight ratio; and   treating the metal mixture at an elevated temperature.   
     
     
         12 . The process according to  claim 10 , wherein the sintering of the mixture includes spark plasma sintering or pressure sintering. 
     
     
         13 . The process according to  claim 11 , wherein the treatment of the metal mixture at the elevated temperature includes using an electric arc. 
     
     
         14 . The process according to  claim 10 , wherein the forming of the particles includes using a ball mill. 
     
     
         15 . The process according to  claim 10 , wherein the process is at least partly carried out in an inert gas atmosphere. 
     
     
         16 . The material according to  claim 2 , wherein the at least one semi-Heusler allow has particles having an average particle size D 50  in the range from ≧10 nm to ≦30 nm. 
     
     
         17 . The material according to  claim 2 , wherein the at least one semi-Heusler allow has particles having an average particle size D 50  in the range from ≧15 nm to ≦20 nm. 
     
     
         18 . The material according to  claim 7 , wherein at least one semi-Heusler alloy is formed based on a composition from the group consisting of Ti 0.64 Zr 0.18 Hf 0.14 Nb 0.04 NiSn, Ti 0.39 Zr 0.28 Hf 0.29 Nb 0.04 NiSn and Ti 0.17 Zr 0.4 Hf 0.39 Nb 0.04 NiSn. 
     
     
         19 . The material according to  claim 9 , wherein at least one semi-Heusler alloy is formed based on a composition from the group consisting of Ti 0.68 Zr 0.18 Hf 0.14 NiSn 0.998 Sb 0.002 , Ti 0.43 Zr 0.28 Hf 0.29 NiSn 0.998 Sb 0.002  and Ti 0.21 Zr 0.4 Hf 0.39 NiSn 0.998 Sb 0.002 .