【报告时间】2017年7月14日上午10:00-11:30
【报告地点】玉泉校区曹光彪科技大楼326会议室
【报告题目】Origin of low thermal conductivity in complex chalcogenides: Effect ofintergrowth nanostructures, point defects, lone pair and rattling
【报告人】Kanishka Biswas
Kanishka Biswas obtained his MS and Ph.D degree from the Solid State Structural Chemistry Unit, Indian Institute of Science (2009) under supervision of Prof. C. N. R. Rao and did postdoctoral research with Prof. Mercouri G. Kanatzidis at the Department of Chemistry, Northwestern University (2009–2012). He is an Assistant Professor in the New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bangalore. He is pursuing research in solid state inorganic chemistry of metal chalcogenides, thermoelectrics, topological materials, 2D nanosheets and water purification. He has published 90 research papers, 1 book and 4 book chapters. He is an Young Affiliate of The Third World Academy of Sciences (TWAS) and an Associate of Indian Academy of Science (IASc), Bangalore, India. He is also recipient of Young Scientist Medal-2016 from Indian National Science Academy (INSA), Delhi, India and Young Scientist Platinum Jubilee Award-2015 from The National Academy of Sciences (NASI), Allahabad, India. He is recipient of IUMRS-MRS Singapore Young Researcher Merit Awards in 2016. He is recipient of Materials Research Society of India Medal in 2017.
【报告摘要】
One of the fundamental challenges in developing high-performance thermoelectric materials has been to achieve low lattice thermal conductivity (κL). The exploration of new materials with intrinsically low κL along with a microscopic understanding of the underlying correlations among bonding, lattice dynamics and phonon transport is fundamentally important towards designing promising thermoelectric materials. The origin of lattice anharmonicity and the ensuing ultralow κLin the I-V-VI2chalcogenides such as AgSbSe2, AgBiSe2, AgBiS2and AgBiSeS has been traced to the electrostatic repulsion between the stereochemically active ns2lone pair of group V cation and the valence p-orbital of group VI anion.1InTe [i.e. In+In3+Te2], a mixed valent compound, exhibit an ultralow κL, which manifests an intrinsic bonding asymmetry with coexistent covalent and ionic substructures.2The phonon dispersion of InTe exhibits, in addition to low-energy flat branches, weak instabilities associated with the rattling vibrations of In+atoms along the columnar ionic substructure. These weakly unstable phonons originate from the 5s2lone pairs of adjacent In+ atoms and are strongly anharmonic, which scatter the heat-carrying acoustic phonons through phonon-phonon interactions. Similarly, a Zintl compound, TlInTe2, also exhibit ultralow κL due to low energy ratting modes of weakly bound Tl.3Formation of layered 2D intergrowth nanostructures in solid matrix by kinetic matrix encapsulation can also lead to ultralow κL.4Further, pseudo-ternary system (GeTe-GeSe-GeS) exhibit extended solids solution due higher entropy over enthalpy, gives rise to low κL and large thermoelectric figure of merit (zT) of 2.1 at 625 K.5
1. S. N. Guin, A. Chatterjee, D. S. Negi, R. Datta, and K. Biswas, Energy Environ. Sci. 2013, 6, 2603.
2. M. K. Jana, K. Pal, U. V. Waghmare, and K. Biswas, Angew. Chem Int. Ed, 2016, 55, 7792.
3. M. K. Jana, K. Pal, A. Warankar, P. Mandal, U. V. Waghmare, and K. Biswas, J. Am. Chem.
Soc., 2017. 139, 4350–4353.
Soc., 2017. 139, 4350–4353.
4. A. Banik, B. Vishal, S. Perumal, R. Datta, and K. Biswas, Energy Environ. Sci. 2016, 9, 2011. 5. M. Samanta and K Biswas, J. Am. Chem. Soc., 2017 doi: 10.1021/jacs.7b05143
