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Wide gap semiconductors as the thermoelectric (TE) candidates have been increasingly interested because of their inherent high Seebeck coefficients and low thermal conductivities. Ga2Te3 is one of the typical defect compounds (Eg=1.65 eV) among the A2IIIB3VI type semiconductors, in which there are periodically self-assembled 2D vacancy planes that wrap the nanostructured domains. The vacancy planes scatter phonons highly effectively and are responsible for reducing the lattice thermal conductivity. Hence Ga2Te3 might be a good TE candidate. In the phase diagram of Ga-Te, Ga2Te3 is involved in the eutectoid and peritectic reactions at the critical temperatures (CTs) of 680 10 K and 757 10 K respectively. These reactions would lead to the generation of enthalpies of reactions, and induce the alteration of some thermo-physical properties. In the present work, we have not observed the phase transformations at CTs in the Ga2Te3-based materials with sulfur isoelectronic substitution for Te, which are prepared by powder metallurgy with the spark plasma sintering (SPS) technique, but can observe the generation of assumed enthalpies of reactions near CTs, which directly gives rise to the critical acoustic charge transport behaviors. The critical behaviors involve the remarkable increase of heat capacities and Seebeck coefficients and, at the same time, reductions of thermal diffusivities (thermal conductivities) and electrical conductivities. For example, the Seebeck coefficient () at x=0.05 increases rapidly from 376.3(VK-1) to 608.2(VK-1) when the temperature rises from 596 to 695 K, and then decreases to 213.8(VK-1) at 764 K. Similarly, all the S-doped samples, which have lowest electrical conductivities ( ) of 2.12102 (x=0.05), 0.25102 (x=0.1), 0.12102 -1m-1 (x=0.2) and 0.14102 -1m-1 (x=0.3) at 696725 K, undergo dramatic changes when the temperature rises to about 750 K, and then the electrical conductivities begin to decrease, and the changes tend to slow down. It is notable that both the Seebeck coefficients and electrical conductivities exhibit a typical zigzag temperature dependence in the temperature range from 596 to 812 K. These behaviors reveal the remarkable alterations in scattering mechanism of both phonons and carriers at temperatures near the CTs. Although the materials with these critical behaviors near CTs do not have satisfactory thermoelectric performance (ZTmax=0.17 at 793 K for x=0.3) as compared with the known binary Cu2Se, Ag2Se(S) or ternary based AgCrSe2 alloys, however, the findings of such critical transport behaviors have a great significance for future researches.
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Keywords:
- thermoelectric materials /
- wide gap /
- Ga2Te3 /
- critical acoustic charge transport
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[2] Guymont M, Tomas A, Guittard M 1992 Philos. Mag. 66 133
[3] Finkman E, Tauc J, Kershaw R, Wold A 1975 Phys. Rev. B 11 3785
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[11] Liu H, Yuan X, Lu P, Shi X, Xu F, He Y, Tang Y, Bai S, Zhang W, Chen L, Lin Y, Shi L, Lin H, Gao X, Zhang X, Chi X, Uher, C 2013 Adv. Mater. 25 6607
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[13] Capps J, Drymiotis F, Lindsey S, Tritt T M 2010 Philos. Mag. Lett. 90 677
[14] Wu C, Feng F, Feng J, Dai J, Peng L, Zhao J, Yang J, Si C, Wu Z, Xie Y 2011 J. Am. Chem. Soc. 133 13798
[15] Wang Q, Qin X 2012 Proc. Eng. 27 77
[16] Rao Z H, Wang S F, Zhang Y L, Peng F F, Cai S H 2013 Acta Phys. Sin. 62 056601(in Chinses) [饶中浩, 汪双凤, 张艳来, 彭飞飞, 蔡颂恒 2012 61 056601]
[17] Hu G X, Qian M G 1980 Metallography (Shanghai: Shanghai Scientific and Technical Publishers) p350 (in Chinese) [胡庚祥, 钱苗根 1980 金属学 (上海: 上海科学技术出版社) (上海: 上海科学技术出版社) 第350页]
[18] Gascoin F, Maignan A 2011 Chem. Mater. 23 2510
[19] Gascoin F, Ottensmann S, Stark D, Hale S M, Snyder G J 2005 Adv. Func. Mater. 15 1860
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[1] Guizzetti G, Meloni F 1982 Luglio-Agosto 1D 503
[2] Guymont M, Tomas A, Guittard M 1992 Philos. Mag. 66 133
[3] Finkman E, Tauc J, Kershaw R, Wold A 1975 Phys. Rev. B 11 3785
[4] Kurosaki K, Matsumoto H, Charoenphakdee A, Yamanaka S, Ishimaru M, Hirotsu Y 2008 Appl. Phys. Lett. 93 012101
[5] Cui J L, Gao Y L, Zhou H, Li Y P, Meng Q S, Yang J F 2012 Appl. Phys. Lett. 101 081908
[6] Fu H, Ying P Z, Cui J L, Yan Y M, Zhang X J 2011 Rare Metal Mater. Eng. 40 849 (in Chinese) [付红, 应鹏展, 崔教林, 颜艳明, 张晓军 2011 稀有金属材料与工程 40 849]
[7] Tian D, Liu H, Deng Y, Du Z, Cui J L 2014 RSC Adv. 4 34104
[8] Wuyts K, Watte J, Langouche G, Silverans R E, G. Zgb, Jumas J C 1992 J. Appl. Phys. 71 744
[9] Wang Z, Li H, Su X, Tang X 2011 Acta Phys. Sin. 60 027202(in Chinses) [王作成, 李涵, 苏贤礼, 唐新峰 2011 60 027202]
[10] Zhang X, Ma X Y, Zhang F P, Wu P X, Lu Q M, Liu Y Q, Zhang J X 2012 Acta Phys. Sin. 61 047201(in Chinses) [张忻, 马旭颐, 张飞鹏, 武鹏旭, 路清梅, 刘燕琴, 张久兴 2012 61 047201]
[11] Liu H, Yuan X, Lu P, Shi X, Xu F, He Y, Tang Y, Bai S, Zhang W, Chen L, Lin Y, Shi L, Lin H, Gao X, Zhang X, Chi X, Uher, C 2013 Adv. Mater. 25 6607
[12] Xiao C, Xu J, Li K 2012 J. Am. Chem. Soc. 134 4287
[13] Capps J, Drymiotis F, Lindsey S, Tritt T M 2010 Philos. Mag. Lett. 90 677
[14] Wu C, Feng F, Feng J, Dai J, Peng L, Zhao J, Yang J, Si C, Wu Z, Xie Y 2011 J. Am. Chem. Soc. 133 13798
[15] Wang Q, Qin X 2012 Proc. Eng. 27 77
[16] Rao Z H, Wang S F, Zhang Y L, Peng F F, Cai S H 2013 Acta Phys. Sin. 62 056601(in Chinses) [饶中浩, 汪双凤, 张艳来, 彭飞飞, 蔡颂恒 2012 61 056601]
[17] Hu G X, Qian M G 1980 Metallography (Shanghai: Shanghai Scientific and Technical Publishers) p350 (in Chinese) [胡庚祥, 钱苗根 1980 金属学 (上海: 上海科学技术出版社) (上海: 上海科学技术出版社) 第350页]
[18] Gascoin F, Maignan A 2011 Chem. Mater. 23 2510
[19] Gascoin F, Ottensmann S, Stark D, Hale S M, Snyder G J 2005 Adv. Func. Mater. 15 1860
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