High performance thermoelectric materials and methods of preparation

A thermoelectric device comprising:

• a first material having the formula:
• Co.sub.1-x-y Rh.sub.x Ir.sub.y Sb.sub.3
• wherein 0.ltoreq.x.ltoreq.1 and 0.ltoreq.y.ltoreq.1;
• and
• a second material selected from the group consisting of Bi-Sb alloys, Bi.sub.2 Te.sub.3 based alloys, PbTe based alloys, .beta.-FeSi.sub.2 based alloys, Ga.sub.1-x In.sub.x Sb based alloys, and SiGe alloys.

A thermoelectric device having a plurality of thermoelectric elements formed from at least two different types of semiconductor materials comprising:

• a portion of the thermoelectric elements formed from P-type semiconductor material having a skutterudite-type crystal lattice structure;
• and
• the P-type semiconductor material having the formula:
• Co.sub.1-x-y Rh.sub.x Ir.sub.y Sb.sub.3
• wherein 0.ltoreq.x.ltoreq.1 and 0.ltoreq.y.ltoreq.1.

Apparatus using gradient freeze techniques to prepare a semiconductor alloy for use in fabricating thermoelectric elements comprising:

• a furnace defined in part by a housing having a chamber with a first heater and a second heater disposed therein;
• the first heater disposed within the chamber above the second heater;
• a thermal baffle disposed within the chamber between the first heater and the second heater;
• a container disposed within the chamber with the container adjacent to the thermal baffle;
• a plurality of elemental materials disposed within the container for melting within the furnace to form the desired semiconductor alloys;
• a sealed vessel with a first elemental material and a second elemental material;
• and
• the first elemental material selected from the group consisting of iridium, rhodium and cobalt, and the second elemental material comprising antimony.

Apparatus using liquid-solid phase sintering techniques to prepare a semiconductor alloy for use in fabricating thermoelectric elements comprising:

• an isothermal furnace defined in part by a housing having a chamber with a heater disposed therein;
• a container disposed within the chamber, with the container spaced intermediate from the interior surfaces of the chamber;
• and
• a stoichiometric mixture of elemental materials selected from the group consisting of Co, Rh, Ir and Sb disposed within the container for forming polycrystalline ingots.

A method of preparing a semiconductor alloy having a skutterudite-type crystal lattice structure for use in fabricating thermoelectric elements comprising the steps of:

• placing a first material selected from the group consisting of Ir, Rh and Co, and a second material comprising antimony in a container;
• placing the container within a furnace with the second material vertically disposed above the first material;
• heating the furnace to a preselected temperature to allow liquid-solid phase sintering of the first material and the second material;
• and
• retaining the container within the furnace for a preselected length of time to allow formation of polycrystalline ingots of the semiconductor alloy having the desired skutterudite-type crystal lattice structure.

A method of preparing a semiconductor alloy having a skutterudite-type crystal lattice structure for use in fabricating thermoelectric elements comprising the steps of:

• placing a first material selected from the group consisting of Ir, Rh and Co, and a second material comprising antimony in a container;
• placing the container with the first material and second material vertically disposed within a furnace having two heaters;
• heating the furnace to establish a preselected temperature gradient to melt the first and second materials to form a liquid and to grow a semiconductor crystal from the liquid by gradient freeze techniques;
• and
• retaining the container within the furnace for a preselected length of time to allow growing the crystal of the semiconductor alloy having the desired skutterudite-type crystal lattice structure.

A method of preparing a semiconductor alloy for use in fabricating thermoelectric elements from an approximately stoichiometric mixture comprising the steps of:

• placing elemental powders selected from the group consisting of Ir, Rh, Co and Sb in a container to form the mixture;
• placing the container with the mixture within an isothermal furnace;
• and
• retaining the container and the mixture within the isothermal furnace for a preselected length of time to allow formation of the semiconductor alloyed powders having a skutterudite-type crystal lattice structure.

A method of preparing a semiconductor alloy for use in fabricating thermoelectric elements from an approximately stoichiometric mixture comprising the steps of:

• placing elemental powders selected from the group consisting of Ir, Rh, Co, and Sb in a container to form the mixture;
• placing the container with the mixture into an isothermal furnace having a press;
• and
• applying pressure to the mixture with the press for at least 30 minutes while maintaining the temperature of the isothermal furnace at a temperature of at least 600.degree. C. to form polycrystalline pellets having a skutterudite-type crystal lattice structure from the mixture.

A radioisotope thermoelectric generator having a general purpose heat source and a cooling assembly with a thermoelectric device disposed therebetween comprising:

• a plurality of thermoelectric elements formed from at least two different types of semiconductor materials comprising:
• a portion of the thermoelectric elements formed from a P-type semiconductor material having a skutterudite-type crystal lattice structure;
• and
• the P-type semiconductor material having the formula:
• Co.sub.1-x-y Rh.sub.x Ir.sub.y Sb.sub.3
• wherein 0.ltoreq.x.ltoreq.1 and 0.ltoreq.y.ltoreq.1.