Thermoelectric and Magnetic Properties of Pt-Substituted BaFe 4Àx Pt x Sb 12 Compounds MURAT SERTKOL , 1,5 SEDAT BALLIKAYA, 2,3,6 FATIH AYDOG ˘ DU, 4,7 ADIL GU ¨ LER, 4,8 MUSTAFA O ¨ ZDEMIR, 4,9 and YILDIRHAN O ¨ NER 1,10 1.—Department of Physics Engineering, Istanbul Technical University, 34469 Maslak, Turkey. 2.—Department of Physics, Istanbul University, Vezneciler, 34134 Istanbul, Turkey. 3.—Department of Physics, University of Michigan, Ann Arbor, MI, USA. 4.—Department of Physics, Marmara University, Go ¨ztepe, 34722 Istanbul, Turkey. 5.—e-mail: msertkol@itu.edu.tr. 6.—e-mail: sedatb@umich.edu. 7.—e-mail: kahramanfatih24@hotmail.com. 8.—e-mail: asguler@ hotmail.com. 9.—e-mail: mustafaozdemir@marmara.edu.tr. 10.—e-mail: oner@itu.edu.tr BaFe 4Àx Pt x Sb 12 (x = 0, 0.1, 0.2) compounds were prepared by melting and annealing, followed by a spark plasma sintering method. Low-temperature thermoelectric and magnetic properties were investigated based on Seebeck coefficient, electrical and thermal conductivity and magnetization measure- ments. The structural properties of BaFe 4Àx Pt x Sb 12 (x = 0, 0.1, 0.2) compounds were ascertained by powder x-ray diffraction analysis, confirming that all samples have a main phase of a skutterudite structure with the space group Im  3. The lattice parameters obtained, 9.202(5), 9.199(5) and 9.202(1) A ˚ for x = 0, 0.1 and 0.2, respectively, were found consistent with literature. The Seebeck coefficient sign shows that holes are dominant carriers in all compounds. The local maximum Seebeck coefficient was observed around 50 K which may be a trace of paramagnon-drag effect of charge carriers. Thermal conductivity and electrical resistivity measurements were carried out between 4.2 K and 300 K. Temperature dependence of electrical resistivity reflects that all samples show semi-metallic behavior in our temperature range of 4.2–300 K. Samples for x = 0.1 and x = 0.2 show Kondo-like behavior. In magnetization measurement, we observe that there are two successive magnetic transitions in Pt-substituted compounds; however, there is only one (transition from a paramagnetic state to long-range magnetic ordering) in Pt-free compounds. In Pt-substituted compounds, the first transition appears at T c = 48 K. In addition, the second transition is observed at T irr = 30 K where an intermediate state is observed before the magnetic ordering transforms to an irreversible ferromagnetic state. We concluded that Pt substitution on the Fe side effectual on the thermoelectric and magnetic properties of BaFe 4Àx Pt x Sb 12 (x = 0, 0.1, 0.2) compounds. Key words: Skutterudites, paramagnon drag effect, magnetization, thermo electric effect INTRODUCTION Today, an important part of energy used in all worlds is released to the atmosphere as industrial waste heat. Using thermoelectric (TE) materials, it is possible to capture a part of this wasted energy and convert it into useful electrical power. 1,2 The efficiency of a TE generator is strongly dependent on the dimensionless figure of merit ZT, defined as ZT = S 2 rT=j where S, r and j are the Seebeck coefficient, electrical conductivity, total thermal conductivity (j = j e + j L where j e is the electronic contribution and j L the lattice contribution), (Received May 14, 2016; accepted August 4, 2016) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-016-4855-0 Ó 2016 The Minerals, Metals & Materials Society