Abstract
The effect of native defects originated by a non-stoichiometric variation of composition in CoSb3 on I-V curves and Hall effect was investigated. Hysteretic and a non-linear behavior of the I-V curves at cryogenic temperatures were observed; the non-linear behavior originated from the Poole-Frenkel effect, a field-dependent ionization mechanism that lowers Coulomb barriers and increases emission of charge carriers, and the hysteresis was attributed to the drastic decrease of specific heat which produces Joule heating at cryogenic temperatures. CoSb3 is a narrow gap semiconductor and slight variation in the synthesis process can lead to either n- or p-type conduction. The Sb-deficient CoSb3 presented an n-type conduction. Using a single parabolic model and assuming only acoustic-phonon scattering the charge transport properties were calculated at 300 K. From this model, a carrier concentration of 1.18 × 1018 cm−3 and a Hall factor of 1.18 were calculated. The low mobility of charge carriers, 19.11 cm2/V·s, and the high effective mass of the electrons, 0.66 m0, caused a high resistivity value of 2.75 × 10−3 Ω·m. The calculated Lorenz factor was 1.50 × 10−8 V2/K2, which represents a decrease of 38% over the degenerate limit value (2.44 × 10−8 V2/K2).
Highlights
Thermoelectric (TE) materials can generate electric potentials when subjected to a temperature gradient (Seebeck effect) and, they can transfer heat against a temperature gradient when a current is applied against the generated potential (Peltier effect) [1]
The main obstacle to widespread use of thermoelectric TE materials is their low efficiency for converting thermal energy into electric energy [2]
The performance of a TE material is related to the dimensionless thermoelectric figure of merit, ZT, defined as ZT = S2 σT/(κe + κL ), where S is the Seebeck coefficient, T is the absolute temperature, σ is the electrical conductivity, κe and κL are the electronic and lattice thermal conductivities, respectively
Summary
Thermoelectric (TE) materials can generate electric potentials when subjected to a temperature gradient (Seebeck effect) and, they can transfer heat against a temperature gradient when a current is applied against the generated potential (Peltier effect) [1]. The performance of a TE material is related to the dimensionless thermoelectric figure of merit, ZT, defined as ZT = S2 σT/(κe + κL ), where S is the Seebeck coefficient, T is the absolute temperature, σ is the electrical conductivity, κe and κL are the electronic and lattice thermal conductivities, respectively. Skutterudites are good examples of the phonon-glass-electron-crystal (PGEC) concept proposed by Slack [4] in 1995 and, they are regarded as promising candidates for next-generation TE materials for electrical power generation using either solar energy or waste heat [10]. Deviation from stoichiometry in skutterudites is a common issue that can result in a large variation in electrical transport properties (i.e., Seebeck coefficient and electrical conductivity) [11]. The focus has been to study the influence of native defects on charge transport properties
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