Structural features and thermoelectric performance of chalcopyrite Cu(In, Ga)Te2 system by isoelectronic substitution

In this paper, a series of CuIn1-xGaxTe2 samples were prepared by vacuum melting combined with the spark plasma sintering process based on the initial stoichiometric ratios of 1: 1-x: x: 2 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0). Crystal results indicate that all Cu(In, Ga)Te2 system samples are the chalcopyrite structure with space group I4‾2d. Thermal analysis results show that all the samples have excellent reproducibility and thermal stability. EPMA data indicates that Ga tended to replace In site instead of Cu or Te. Meanwhile, the room-temperature carrier concentration of all p-type samples varies from 0.30 × 1019 to 1.25 × 1019cm−3, since carrier mobility changes from 15.16 to 69.27 cm2 V−1 s−1. Ultimately, the significantly reduced total thermal conductivity is observed in the Ga-doped samples, and the maximum ZT value of 0.80 is obtained at 773 K for the CuIn0.8Ga0.2Te2 sample due to the lower thermal conductivity. Figure 1 displays temperature dependence of the figure of merit ZT of all Ga-doped CuInTe2 samples. The significantly reduced total thermal conductivity is observed in the Ga-doped samples compared with the pure CuInTe2 sample, a high ZT of 0.80 is achieved in the Ga-doped sample with x = 0.2 at 773 K. The work provides an insight into the effective solution employed to enhance ZT, which would be instructive for other materials systems via the doping with different atoms. [Display omitted] •CuIn1-xGaxTe2 samples were prepared by vacuum melting and the spark plasma sintering process.•The obtained samples possess the excellent reproducibility and thermal stability.•The lower thermal conductivity is achieved in the Ga doped sample.•The maximum ZT value of 0.80 is obtained at 773 K for the CuIn0.8Ga0.2Te2.•The work provides an insight into the effective solution employed to enhance ZT.