Systematic investigation on transverse thermoelectric conversion of RE₂(Fe,Co)₁₄B (RE = rare-earth) compounds

Transverse thermoelectric generation (TEG) based on the anomalous Nernst effect (ANE) is a promising technology capable of converting waste heat into electricity. The transverse TEG device can operate without applying an external magnetic field by implementing permanent magnets, such as Nd₂Fe₁₄B-type magnets. However, the transverse thermoelectric properties of the rare-earth (RE) based compounds have not been systematically studied and understood so far. In this work, we have explored the potential of RE₂Fe₁₄B and Nd₂(Fe, Co)₁₄B compounds and systematically investigated the transverse thermoelectric properties at room temperature. We obtained the negative anomalous Nernst coefficient (<i>S</i>_ANE) for all the RE₂Fe₁₄B (RE=Tb, Dy, Ho, and Nd) alloys regardless of the RE element and the highest negative <i>S</i>_ANE of -0.67× 10⁻⁶ VK⁻¹ for Tb₂Fe₁₄B among them, which is comparable to that of the commercial Nd₂Fe₁₄B permanent magnets with an optimized microstructure. The substitution of Co for Fe site in Nd₂(Fe_1-<i>p</i>Co_<i>p</i>)₁₄B alloys causes sign reversal (from negative to positive) of <i>S</i>_ANE values. The transverse thermoelectric conductivity is responsible for the sign change in <i>S</i>_ANE values. As a result, the Nd₂(Fe_0.4Co_0.6)₁₄B alloy shows the highest positive <i>S</i>_ANE of 1.87 × 10⁻⁶ VK⁻¹, revealing that the RE and 3<i>d</i> transition metal elements play the distinct roles on the transverse thermoelectric performance in RE₂(Fe,Co)₁₄B compounds. This work systematically investigates rare-earth-based RE₂Fe₁₄B compounds, uncovering tunable transverse thermoelectric properties, including anomalous Nernst coefficient sign reversal and a 2-fold enhancement via Co substitution, advancing efficient transverse thermoelectric generation technologies.