Abstract
Cubic AgSbTe2 compound is a metastable phase within Ag2Te-Sb2Te3 pseudo-binary phase diagram and theoretically rapid cooling molten elements to room temperature may be an effective way to obtain it. In this work, thick films composed of 5–10 nm fine grains were developed by a melt spinning technique. The formation mechanism of the nanostructure and its influences on the thermoelectric properties have been studied and correlated. Differential scanning calorimetry (DSC) analysis shows that the as-prepared films exhibit distinct thermodynamic properties when prepared under different cooling rates and doping element. A small amount of Se doping is effectively capable of inhibiting the emergence of the Ag2Te impurity and optimizing the electrical transport properties. All films have positive large Seebeck coefficient, but rather small positive or negative Hall coefficient, indicating a multicarrier nature of transport consisting of both holes and electrons. A power factor of ~1.3 was achieved at 500 K for Se-doped film for its excellent electrical conductivities. This result confirms that a combination of Se doping and melting spinning technique is an effective way to obtain high phase-pure AgSbTe2 compound and reveal its intrinsic transport properties routinely masked by impurities in sintering or slow-cooling bulk samples.
Highlights
Thermoelectric materials are capable of converting waste heat from industry and vehicles into useful electricity [1]
Selenium was chosen as a dopant because previous work displayed that 1% of Se is capable of inhibiting the formation of AgTe2 impurities and improving the thermoelectric properties in bulk samples prepared by spark plasma sintering [9,14]
Rather than focusing on bulk sintered samples, we investigated the microstructure and transport properties of AgSbTe2 thick films developed by melt spinning, and discussed the effects of Se doping and cooling rate on their structural, thermodynamic, and transport properties
Summary
Thermoelectric materials are capable of converting waste heat from industry and vehicles into useful electricity [1]. AgSbTe2 compound is the common end component of famous thermoelectric systems (AgSbTe2)1−x(GeTe)x [7] and (AgSbTe2)1−x(PbTe)x [3], and has the highest figure-of-merit zT of all simple ternary compounds [4,8,9,10]. It has a large Seebeck coefficient and a low thermal conductivity, because of the complexity of ordering of Ag/Sb on the face-centered lattice and strong lattice vibrational anharmonicity [11,12,13]. In 2008, Wang et al [10] reported a zT of 1.59 by mechanical alloying, and Du et al [4] followed with a zT of 1.65 by a melt-spinning-spark-plasma-sintering synthesis route in 2011
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