A magnesium-based thermoelectric conversion material includes a first layer formed of Mg.sub.2Si and a second layer formed of Mg.sub.2Si.sub.xSn.sub.1-x (here, x is equal to or greater than 0 and less than 1), in which the first layer and the second layer are directly joined to each other, and within a junction surface with the first layer and in the vicinity of the junction surface, the second layer has a tin concentration transition region in which a tin concentration increases as a distance from the junction surface increases. The junction layer is regarded as a site in which a tin concentration is found to be equal to or lower than a detection limit by the measurement performed using EDX.

Provided is a thermoelectric material having an intermetallic compound in an Al—Fe—Si system as a main component, exhibiting a thermoelectric effect in a temperature range from a room temperature to 600° C., and becoming a p-type or n-type thermoelectric material by a composition control, a manufacturing method thereof, and a thermoelectric power generation module thereof. A thermoelectric material according to the present invention including at least Al, Fe, and Si and represented by a general formula of Al.sub.12+p−qFe.sub.38.5+3qSi.sub.49.5−p−2q (where p satisfies 0≤p≤16.5 and q satisfies −0.34≤q≤0.34) and including a phase represented by Al.sub.2Fe.sub.3Si.sub.3 as a main phase.

Methods of making various fibers are provided including co-axial fibers with oppositely doped cladding and core are provide; hollow core doped silicon carbide fibers are provided; and doubly clad PIN junction fibers are provided. Additionally methods are provided for forming direct PN junctions between oppositely doped fibers are provided. Various thermoelectric generators that incorporate the aforementioned fibers are provided.

A thermoelectric element according to one embodiment of the present disclosure includes a first substrate, a first resin layer disposed on the first substrate, a first electrode disposed on the first resin layer, a P-type thermoelectric leg and an N-type thermoelectric leg disposed on the first electrode, a second electrode disposed on the P-type thermoelectric leg and the N-type thermoelectric leg, a second resin layer disposed on the second electrode, and a second substrate disposed on the second resin layer, wherein at least one of the first electrode and the second electrode includes a copper layer, first plated layers disposed on both surfaces of the copper layer, and second plated layers disposed between both surfaces of the copper layer and the first plated layers, materials of the first plated layer and the second plated layer are different from each other, and the first plated layer has a melting point greater than or equal to 300° C., and an electrical conductivity greater than or equal to 9×10.sup.6 S/m.

A thermoelectric material includes a parent phase in which an MgSiSn alloy is a main component, a void formed in the parent phase, and a silicon layer that is formed on at least a wall surface of the void and that includes silicon as a main component. The thermoelectric material further includes MgO in an amount of 1.0 wt. % or more and 20.0 wt. % or less. The silicon layer includes amorphous Si, or amorphous Si and nanosized Si crystals, and the parent phase includes a region in which the composition ratio of the Si of the chemical composition of the MgSiSn alloy is higher than in the other regions and a region in which the composition ratio of the Sn of the chemical composition of the MgSiSn alloy is higher than in the other regions. With these configurations, the thermoelectric material realizes both lower thermal conductivity and lower electrical resistivity.

A device including a liquid's flow path having an upstream side and a downstream side, a plurality of flow restrictive elements providing material communication between the upstream side to the downstream side, a thermoelectric generator or a thermophotovoltaic cell in thermal connection with a portion of the device located at the downstream side with respect to the plurality of flow restrictive elements. The portion is provided with roughness elements for, in use, contacting a fluid flowing through the device and facilitating collapse of cavitation bubbles.

There is provided a thermoelectric conversion material in which a first layer containing Mg.sub.2Si.sub.xSn.sub.1-x (here, 0<x<1) is directly joined to a second layer containing Mg.sub.2Si.sub.ySn.sub.1-y (here, 0<y<1), where x/y is set within a range of more than 1.0 and less than 2.0. There is also provided a thermoelectric conversion element including the thermoelectric conversion material and electrodes each joined to one surface and the other surface of the thermoelectric conversion material. There is also provided a thermoelectric conversion module including terminals each joined to the electrodes of the thermoelectric conversion element.

There is provided a thermoelectric conversion material in which a first layer containing Mg.sub.2Si.sub.xSn.sub.1-x (here, 0<x<1) is directly joined to a second layer containing Mg.sub.2Si.sub.ySn.sub.1-y (here, 0<y<1), where x/y is set within a range of more than 1.0 and less than 2.0. There is also provided a thermoelectric conversion element including the thermoelectric conversion material and electrodes each joined to one surface and the other surface of the thermoelectric conversion material. There is also provided a thermoelectric conversion module including terminals each joined to the electrodes of the thermoelectric conversion element.

A semiconductor sintered body comprising a polycrystalline body, wherein the polycrystalline body includes silicon or a silicon alloy, wherein the average grain size of the crystal grains forming the polycrystalline body is 1 μm or less, and wherein nanoparticles including one or more of a carbide of silicon, a nitride of silicon, and an oxide of silicon are present at a grain boundary of the grains.

A thermionic energy converter, preferably including an anode and a cathode. An anode of a thermionic energy converter, preferably including an n-type semiconductor, one or more supplemental layers, and an electrical contact. A method for work function reduction and/or thermionic energy conversion, preferably including inputting thermal energy to a thermionic energy converter, illuminating an anode of the thermionic energy converter, thereby preferably reducing a work function of the anode, and extracting electrical power from the system.