Thermoelectric Borides: Review and Future Perspectives

Abstract

The conversion of waste heat into electricity plays a vital role in energy harvesting since conventional non‐renewable energy sources have been rapidly approaching the limit of utilization. The thermoelectric (TE) technology relies on converting temperature difference (or waste heat) into electricity or vice versa. The performance of TE materials is gauged by zT = S2T/ρκ, where S, ρ, κ, and T represent the Seebeck coefficient, the electrical resistivity, the total thermal conductivity, and the absolute temperature, respectively. Boron‐based compounds are considered refractory materials due to their high melting points and advanced chemical and mechanical stability. Besides high thermal stability, many borides exhibit intrinsically low thermal conductivity. The discovery of good TE efficiency in boron carbides, where unexpectedly high Seebeck coefficients (S(T) ≈ 250 µVK−1) are observed at high charge carrier densities (≈1021 cm−3), has induced an intense curiosity for the TE properties of other boron‐based compounds. Intermetallic borides with high boron content (>65 at%) are of particular interest among all known TE materials due to their great potential in TE generators, which can operate under extreme environmental conditions (T > 1000 K). This article reviews the TE properties of borides and state‐of‐art TE materials upon boron/borides doping.

Phase Evolution of Boron Nitride and Carbide during Chemical Vapor Deposition

“…[68][69][70][71][72][73] e thermal stability and availability of B4C gives it good thermoelectric performance at high temperatures, this is why it is considered an important candidate for hightemperature thermoelectric conversion applications. 70,[74][75][76][77][78]…”

On the origin of epitaxial rhombohedral-B4C growth by CVD on 4H-SiC

“…[1][2][3][4] The high boron content and high mechanical and chemical stability have also made BxC a promising candidate for neutron converter layers in solid-state neutron detectors where 10 B converts neutrons to detectable particles. [5][6][7][8][9] Less explored are the optoelectronic [10][11][12][13] and the thermoelectric properties [14][15][16][17][18] of r-BxC, the wide range of composition and material stability 19,20 make the material promising also for radiation-resistant heterostructures and thermoelectric devices respectively. To enable the use of r-BxC in such devices, there is a need to develop and understand thin film deposition processes for high-quality, phase pure epitaxial r-BxC films.…”

Unveiling a Family of Dimerized Quantum Magnets, Conventional Antiferromagnets, and Nonmagnets in Ternary Metal Borides

“…For example, boron nitride is a chemical analogue to carbon; both are expected to adopt similar one-, two-, and three-dimensional structures . Borides are often reported to be suitable for high-temperature ferromagnets, − catalysis, − thermoelectricity, and superhard materials. − Superconductivity has been discovered in magnesium diboride (MgB 2 ). − Nd 2 Fe 14 B is one of today’s best-performing permanent magnets . The formation of binary, ternary, and multinary borides among boron and metal elements provides a rich materials family to explore.…”

“…For example, boron nitride is a chemical analogue to carbon; both are expected to adopt similar one-, two-, and three-dimensional structures. 27 Borides are often reported to be suitable for high-temperature ferromagnets, 28−31 catalysis, 32−34 thermoelectricity, 35 and superhard materials. 36−39 Superconductivity has been discovered in magnesium diboride (MgB 2 ).…”