Sains Malaysiana 47(1)(2018): 181–187

http://dx.doi.org/10.17576/jsm-2018-4701-21

 

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

(Peningkatan Sifat Termoelektrik bagi Bahan Skuterudit Yb0.25Co4Sb12 melalui Penggantian Ni)

 

MOHAMED BASHIR ALI BASHIR1, SUHANA MOHD SAID2*, MOHD FAIZUL MOHD SABRI2, YUZURU MIYAZAKI3, DHAFER ABDUL AMEER SHNAWAH2, MASANORI SHIMADA3 & MOHAMED HAMID ELSHEIKH4

 

 

1Department of Mechanical Engineering, Faculty of Engineering, Eldaein University, 63312 Eldaein, Sudan

 

2University of Malaya, 50603 Kuala Lumpur, Federal Territory, Malaysia

 

3Tohoku University, 2 Chome-1-1 Katahira, Aoba Ward, Sendai, Miyagi Prefecture 980-8577, Japan

 

4R&D, Cree Inc., Durham, NC 27703, USA

 

Received: 28 November 2016/Accepted: 9 June 2017

 

ABSTRACT

In this work, we investigate the effects of Ni doping on the thermoelectric (TE) properties of Yb0.25Co4Sb12 sample. Yb0.25Co4-xNixSb12 (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 Co4Sb12 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 Yb0.25Co3.5Ni0.5Sb12 sample, due to increase of the electron concentration by Ni-addition. The absolute Seebeck coefficient reached the highest value of 223 μV/K at 592 K for Yb0.25Co3.7Ni0.3Sb12 sample, thus yielding a maximum value of power factor of 2.41 × 10-3 W/mK2 at 592 K. The highest dimensionless thermoelectric figure of merit value ZT of 0.49 at 692 K has been achieved for the Yb0.25Co3.7Ni0.3Sb12 sample, compared to ZT=0.06 for the Yb0.25Co4Sb12 sample at same temperature. This work indicates a strategy to improve the thermoelectric performance by Ni substitution of Co sites in the Yb0.25Co4Sb12 skutterudite through simultaneous improvement of its electrical conductivity, Seebeck coefficient and reduction of its thermal conductivity.

 

Keywords: Mechanical alloying; Ni-doping; skutterudite; thermoelectric

 

ABSTRAK

Dalam kajian ini, kesan pendopan Ni ke atas sifat Yb0.25Co4Sb12 telah dikaji. Sampel Yb0.25Co4-xNixSb12 (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 Yb0.25Co4-xNixSb12 CoSb3 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 Yb0.25Co3.5Ni0.5Sb12, disebabkan oleh peningkatan bilangan pembawa cas elektron oleh Ni. Pekali Seebeck mutlak mencapai nilai tertinggi 223 μV/K pada 592 K bagi sampel Yb0.25Co3.7Ni0.3Sb12 , lalu menghasilkan nilai maksimum faktor kuasa 2.41 × 10-3 W/MK2 pada 592 K. Angka merit, ZT yang optimum adalah 0.49 pada 692 K telah dicapai untuk sampel Yb0.25Co3.7Ni0.3Sb12. Kajian ini menunjukkan strategi untuk meningkatkan prestasi termoelektrik melalui penggantian Ni pada bahagian Co dalam bahan skutterudite Yb0.25Co4Sb12, sekaligus menambahbaik kekonduksian elektrik, pekali Seebeck dan pengurangan kekonduksian haba.

 

Kata kunci: Ni-dop; pengaloian mekanikal; skuterudit; termoelektrik

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*Corresponding author; email: smsaid@um.edu.my

 

 

 

 

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