Impact of Ir doping on the thermoelectric transport properties of half-Heusler alloys

Abstract

Abstract Using density functional and and Boltzmann transport theories, we investigate the thermoelectric transport properties <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">ZrCo</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>-</mml:mo> <mml:mi mathvariant="normal">x</mml:mi> <mml:mspace width="0.25em"/> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ir</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">x</mml:mi> </mml:mrow> </mml:msub> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">Sb</mml:mi> </mml:math> (x = 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, 1) half-Heusler alloys. The current work found that increasing the concentration of iridium ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ir</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">x</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) from x = 0 to 0.375 in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">ZrCo</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>-</mml:mo> <mml:mi mathvariant="normal">x</mml:mi> <mml:mspace width="0.25em"/> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ir</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">x</mml:mi> </mml:mrow> </mml:msub> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">Sb</mml:mi> </mml:math> alloys from room temperature to 800 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">K</mml:mi> </mml:math> significantly decreased thermal and electrical conductivity due to a shorter relaxation time. Furthermore, our results show that <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">ZrCo</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0.625</mml:mn> <mml:mspace width="0.25em"/> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ir</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0.375</mml:mn> </mml:mrow> </mml:msub> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">Sb</mml:mi> </mml:math> has the highest Seebeck coefficient (353.93 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">V</mml:mi> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">K</mml:mi> </mml:math> ) at 300 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">K</mml:mi> <mml:mo>,</mml:mo> </mml:math> thereby boosting its thermoelectric performance. Interestingly, the thermoelectric figure of merit (ZT) has exceptional value 1.01 by applying 25% (x = 0.25) of atomic doping of iridium (Ir) with a carrier concentration of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.47</mml:mn> <mml:mo>⋅</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>20</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> at 1000 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">K</mml:mi> </mml:math> and 37.5% (x = 0.375) of atomic doping of iridium (Ir) with a carrier concentration of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>7.23</mml:mn> <mml:mo>⋅</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>19</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> at 800 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">K</mml:mi> <mml:mo>.</mml:mo> </mml:math> Calculations present important results on the suitability of the studied alloys for thermoelectric applications.