Abstract
We investigate the thermoelectric properties of the relatively unexplored rare-earth ternary compounds La3Cu3X4 (X = Bi, Sb, As, and P) using first principles electronic structure and Boltzmann transport calculations. These compounds, of which the La3Cu3Sb4 and La3Cu3Bi4 have previously been synthesized, are all predicted to be semiconductors and present a wide range of bandgaps varying from 0.24 eV (for the Bi compound) to 0.87 eV (for the P compound). We further find a mixture of light and heavy bands, which results in a high thermoelectric power factor. In addition, as discussed in our previous study (Phys. Rev. B 95 (22), 224306, 2017) at high temperatures of 1000 K these compounds exhibit lattice thermal conductivity less than 1 W/mK. The combination of low thermal conductivity and good transport properties results in a predicted ZT as high as ~1.5 for both La3Cu3P4 and La3Cu3As4, under high p-type doping. This predicted high performance makes these compounds promising candidates for high temperature thermoelectric applications and thus merits further experimental investigation.
Highlights
Thermoelectric materials can convert waste heat to useful electricity
Our results make clear that the La based ternary rare earth compounds studied here are quite likely to have high power factor, which together with low κlatt as discussed in ref.[32] results in high figure of merit
In particular we report that a ZT of 1.5 can be achieved for La3Cu3P4 and La3Cu3As4 under p-type doping at a doping level of 7 × 1020 cm−3
Summary
Thermoelectric materials can convert waste heat to useful electricity. The performance of a thermoelectric material is determined by the figure of merit (ZT) given by S2σ , where S is the thermopower, σ is the electrical conducκ tivity, and κ is the thermal conductivity. Mahan and Sofo proposed two decades ago that a delta-function electron density of states distribution near the band edge results in large thermopower[24] This delta function behavior in the density of states can be realized in nature by the f-electron level of the rare earth element in a material[25,26]. YbAl3, exhibits highest power factor among all known thermoelectric materials in the temperature range 100– 300 K27,28 This large factor is attributed to a sharp feature in the density of states near the band edge, which originates from the interaction of Yb 4f electrons with the conduction electrons. We find these compounds to be www.nature.com/scientificreports/
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