Enhancement of Thermoelectric Properties of Yb0.25Co4Sb12 Skutterudites through Ni Substitution

Abstract

In this work, we investigate the effects of Ni doping on the thermoelectric (TE) properties of Yb 0.25 Co 4 Sb 12 sample. Yb 0.25 Co 4x Ni x Sb 12 (0 ≤ x ≤ 0.5) samples were prepared by mechanical alloying and subsequently consolidated by spark plasma sintering. The morphology of consolidated samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS). The thermoelectric properties of bulk samples were measured from room temperature to 800 K. The XRD analysis confirmed that, the successful formation of the Co 4 Sb 12 skutterudite phase and Ni is substituted into Co site of the skutterudite crystal lattice. Moreover, the electrical resistivity decreased to 14.6 μΩm at 785 K for Yb 0.25 Co 3.5 Ni 0.5 Sb 12 sample, due to increase of the electron concentration by Niaddition. The absolute Seebeck coefficient reached the highest value of 223 μV/K at 592 K for Yb 0.25 Co 3.7 Ni 0.3 Sb 12 sample, thus yielding a maximum value of power factor of 2.41 × 10 -3 W/mK 2 at 592 K. The highest dimensionless thermoelectric figure of merit value ZT of 0.49 at 692 K has been achieved for the Yb 0.25 Co 3.7 Ni 0.3 Sb 12 sample, compared to ZT=0.06 for the Yb 0.25 Co 4 Sb 12 sample at same temperature. This work indicates a strategy to improve the thermoelectric performance by Ni substitution of Co sites in the Yb 0.25 Co 4 Sb 12 skutterudite through simultaneous improvement of its electrical conductivity, Seebeck coefficient and reduction of its thermal conductivity. ABSTRAK Dalam kajian ini, kesan pendopan Ni ke atas sifat Yb 0.25 Co 4 Sb 12 telah dikaji. Sampel Yb 0.25 Co 4-x Ni x Sb 12 (0 ≤ x ≤ 0.5) telah disediakan dengan kaedah pengaloian mekanikal dan seterusnya digabungkan dengan pensinteran pencucuh plasma. Morfologi untuk sampel gabungan telah dicirikan oleh pembelauan sinar-X (XRD) dan imbasan mikroskop elektron berserta tenaga serakan X-ray spektroskopi (SEM-EDS). Ciri termoelektrik sampel telah diukur daripada suhu bilik ke 800 K. Analisis XRD mengesahkan bahawa Ni berjaya didopkan ke dalam Yb 0.25 Co 4-x Ni x Sb 12 CoSb 3 dalam fasa skutterudite, dengan Ni menggantikan beberapa lokasi Co dalam kekisi kristal skuterudit. Selain itu, kerintangan elektrik menurun kepada 14.6 μΩm di 785 K bagi sampel Yb 0.25 Co 3.5 Ni 0.5 Sb 12 , disebabkan oleh peningkatan bilangan pembawa cas elektron oleh Ni. Pekali Seebeck mutlak mencapai nilai tertinggi 223 μV/K pada 592 K bagi sampel Yb 0.25 Co 3.7 Ni 0.3 Sb 12 , lalu menghasilkan nilai maksimum faktor kuasa 2.41 × 10 -3 W/MK 2 pada 592 K. Angka merit, ZT yang optimum adalah 0.49 pada 692 K telah dicapai untuk sampel Yb 0.25 Co 3.7 Ni 0.3 Sb 12 . Kajian ini menunjukkan strategi untuk meningkatkan prestasi termoelektrik melalui penggantian Ni pada bahagian Co dalam bahan skutterudite Yb 0.25 Co 4 Sb 12 , sekaligus menambahbaik kekonduksian elektrik, pekali Seebeck dan pengurangan kekonduksian haba.

Unveiling the Structural Behavior under Pressure of Filled M0.5Co4Sb12 (M = K, Sr, La, Ce, and Yb) Thermoelectric Skutterudites

“…The local bonding of the filler inside the cavities plays a pivotal role for enhancing the zT parameter. Rare-earth elements have been usually a common choice to fill these voids, with plenty of examples reported in the literature. − Recently, our group demonstrated that the high-pressure synthesis is an effective tool to stabilize lanthanides into the voids of the □Co 4 Sb 12 skutterudite, as in the case of La, Ce and Yb, and mischmetal, consequently reducing the thermal conductivity (<2–3 Wm –1 K –1 ).…”