Systematic investigation on transverse thermoelectric conversion of RE ₂ (Fe,Co) ₁₄ B (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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>×</mml:mo></mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>×</mml:mo></mml:math> 10^-6 VK^-1, revealing that the RE and 3<i>d</i> transition metal elements play distinct roles on the transverse thermoelectric performance in RE₂(Fe,Co)₁₄B compounds.