Sublimation protection coating for thermoelectric materials and devices
AssigneeThe United States of America as represented by the Secretary of the Army
InventorsPatrick J. Taylor, Jay R. Maddux, Kimberly A. Olver, Sina Simingalam
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Abstract
Protective coating to prevent sublimation are disclosed. More particularly, the protective coatings comprise one or more alkaline earth halide materials, or mixtures thereof, to prevent sublimation. The alkaline earth halide material of the coating can be judiciously selected to match the coefficient of thermal expansion (CTE) of the material of the external surface of the underlying substrate coated. The protective coatings may be advantageous for protecting external surfaces of thermoelectric materials, parts and devices at high temperature to prevent sublimation and material loss.
Claims25
A thermoelectric part comprising:
- a substrate comprising a thermoelectric material which converts thermal energy into a voltage potential having a surface temperature of at least 350° C. during operation of the thermoelectric part;
- and
- a protective coating comprising an alkaline earth halide directly formed on an external surface of the substrate and exposed to an ambient environment,
- wherein the external surface of the substrate, if exposed to the ambient environment at the surface temperature would sublime, but the protective coating prevents sublimation of the external surface of the substrate at the surface temperature, and
- the protective coating has a thickness of less than about 1 μm.
A thermoelectric device comprising:
- semiconductor substrates formed of thermoelectric material which converts thermal energy into a voltage potential having a surface temperature of at least 350° C. during operation of the thermoelectric device, wherein the semiconductor substrates are in parallel and spaced between conductive interconnects, such that when thermal energy is applied to one of the interconnects, there is a temperature difference across the semiconductor substrates which generates a voltage potential,
- wherein external surfaces of the thermoelectric material, if exposed to an ambient environment at the surface temperature would sublime, but have a protective coating comprising an alkaline earth halide and exposed to the ambient environment to prevent sublimation of the external surfaces of the thermoelectric material at the surface temperature, and
- the protective coating has a thickness of less than about 1 μm.
A thermoelectric device comprising:
- semiconductor substrates formed of thermoelectric material which converts thermal energy into a voltage potential having a surface temperature of at least 350 ° C. during operation of the thermoelectric device, wherein the semiconductor substrates are in parallel and spaced between conductive interconnects, such that when thermal energy is applied to one of the interconnects, there is a temperature difference across the semiconductor substrates which generates a voltage potential,
- wherein external surfaces of the thermoelectric material is formed of thermoelectric material selected from the group consisting of:
- PbTe, SnSe, PbSe, CoSb3 and TAGS, and, if exposed to an ambient environment at the surface temperature would sublime, but have a protective coating consisting of an alkaline earth halide selected from the group consisting of:
- MgF2, CaF2, SrF2 and BaF2 and exposed to the ambient environment to prevent sublimation of the external surfaces of the thermoelectric material at the surface temperature.
A method of preventing sublimation comprising:
- providing a substrate comprising a thermoelectric material which converts thermal energy into a voltage potential;
- forming a protective coating comprising an alkaline earth halide on the entire exposed outer surface of the thermoelectric material of the substrate, the protective coating exposed to an ambient environment;
- and
- performing a heat treatment of at least 350° C. after forming the protective coating,
- wherein the protective coating formed prevents sublimation of the outer surface of the thermoelectric material at during the heat treatment, and
- the protective coating has a thickness of less than about 1 μm.
A method of operating a substrate to prevent sublimation comprising:
- operating the substrate with a surface temperature of at least 350° C., wherein the substrate comprises a thermoelectric material which converts thermal energy into a voltage potential,
- wherein outer external surfaces of the thermoelectric material, if exposed to an ambient environment at the surface temperature would sublime, but have a protective coating comprising an alkaline earth halide and exposed to the ambient environment to prevent sublimation of the outer external surfaces of the thermoelectric material at the surface temperature, and
- the protective coating has a thickness of less than about 1 μm.
Dependencies are inferred from the claim text.