Origin of ultra-low thermal conductivity in complex chalcogenides: Effect of intergrowth nanostructures, lone pair, and anharmonic rattling

Transcription

1 Origin of ultra-low thermal conductivity in complex chalcogenides: Effect of intergrowth nanostructures, lone pair, and anharmonic rattling Kanishka Biswas New Chemistry Unit Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR)

2 Chemical aspects of Topological Insulators [Intergrowth layered chalcogenides + chemical doping + electronic transport + magneto-resistance] Overview of our group (Solid state inorganic chemistry) (Metal chalcogenide chemistry) Satya N. Guin Manoj K. Jana Thermoelectrics [Synthesis + Structure + Charge & phonon transport + Phase-transitions] Bi(OAc) 3 + selenourea N + BF - 4 N Ananya Banik Subhajit Roychowdhury Jana et al., Angew. Chem. Int. Ed (in press). Guin et al., Inorg. Chem (in press). Banik et al., Energy Environ. Sci., 2016, 9, Manisha Samanta Ekashmi Rathore Guin et al. Chem. Sci. 2016, 7, 534. Perumal et al. Chem. Mater., 2015, 27, 7171 Roychowdhury et al., Appl. Phys. Lett., 2016, ( In pres). Roychowdhury et al., Angew. Chem. Int. Ed. 2015, 54, Roychowdhury et al., J. Solidstate. Chem. 2016, 233, 199. Chatterjee et al., Angew. Chem. Int. Ed. 2015, 54, 5623 Sujoy Saha Provas Pal Guin et al. J. Mater. Chem. C 2015, 3, Banik et al. Chem. Mater., 2015, 27, 581. Guin et al. J. Mater. Chem. A 2015, 3, 648 Guin, et al. J. Am. Chem. Soc, 2014, 136, Aggarwal et al. Appl. Phys. Lett., 2014, 105, 903. Banik et al. J. Mater. Chem. A 2014, 2, 960 Chatterjee et al., Phys. Chem. Chem. Phys. 2014, 16, Jana et al., Chem. Eur. J, 2013, 19, 9110 Guin et al. J. Mater. Chem. A 2014, 2, 4324 Guin et al. Energy Environ. Sci., 2013, 6, 2603 Guin et al. Chem. Mater., 2013, 25, 3225

3 High TE performance, high mechanical stability & low cost materials Ge, ZT ~ 1.9 Sn, ZT ~ 1.3 AgSbSe 2 ZT ~ 1.2 AgSb 2 ZT ~ 1.8 ZT = thermoelectric figure of merit Nanostructuring / band convergence JNCASR, Bangalore Thermoelectrics Pb, ZT ~ 2.2 (Spark plasma sintered (SPS)) Biswas & Kanatzids, Nature (2012), 489, Northwestern, USA Fundamental chemistry and structure-property correlation Ultra-low thermal conductivity, phase transition & new compounds

4 Thermoelectrics (TE) The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa.

5 Importance of Thermoelectrics Total energy consumption India (2014) World (2014) Coal, Hydro, Nuclear Petroleum, Natural Gas, Coal, 41 % Petroleum, 23 % Biomass & Waste 23 % Electricity Transportation, Industrial, Commercial uses 70 % of utilized energy rejected as waste heat With about ~70 % of the utilized energy being lost as waste heat. ~10-20% conversion to the useful form can have significant impact on overall energy utilization. Thermoelectric materials allow the direct conversion between thermal and electrical energy.

6 Applications Direct Heat to Electricity Conversion Waste Heat Recovery/Power generation Large scale: Power plant Small scale: Automobile Space power generation Cooling/Refrigeration Commercial cooler/warmer Spot cooling: microprocessor, laser diode Luxury vehicle: Cool/warm seat The Mars Science Laboratory rover, Curiosity, is powered by its Radioisotope Thermoelectric Generator. JPL-Caltech/NASA

7 Thermoelectric material Metal High electrical conductivity S Glass Low thermal conductivity Semiconductor High Seebeck Seebeck Coefficient Electrical conductivity 2 S ZT. T G. J. Snyder and E. S. Toberer, Nat. Mater. 2008, 7, Thermal conductivity (electrical + lattice) Best thermoelectric materials: Highly doped narrow band gap semiconductor eg. Bi 2 3, Pb. Decoupling of electrical and phonon transport is essential for thermoelectrics

8 State of art thermoelectric bulk materials 3rd 2nd 1st Commercial materials in market η = 10 % with ZT of 1 Zhao, L. D., Dravid, V. P., Kanatzidis, M. G., Energy Environ. Sci. (2014), 7, 251 Biswas, K.; He, J.; Blum, I. D.; Chun-I, W.; Hogan, T. P.; Seidman, D. N.; Dravid, V. P.; Kanatzidis, M. G., Nature (2012), 489, Pb-free high performance materials are desired for mass-market applications 2 S ZT. T

9 Extrinsic approaches to reduce lattice thermal conductivity

10 Bulk nanostructured thermoelectric materials Decrease the thermal conductivity LAST-m (Ag 0.86 Pb 18 Sb 20 ) n-type Pb Ag-Sb rich M. G. Kanatzidis, et al., Science 303, (2004).

11 Phonon scattering mechanism in thermoelectric material Scattering cross section = d 6 /λ 4 Mid/long wavelength heat-carrying phonon heavily scattered by nanoparticles Vines, C. J., Shakouri, A., Majumdar, A., Kanatzidis, M. G., Adv. Mater 22, 3970 (2010)

12 Sn is a replacement of Pb Similar Crystal Structure and Electronic Structure as Pb Pb Sn L 6 + L K E g = 0.3 ev L 6 - L 6 + E V = eV E g = 0.18 ev E V = 0.35 ev Excess p-type Carrier concentration (10 21 cm -3 ): High electrical and thermal conductivity and Low Seebeck low ZT A. Banik, U. S. Shenoy, S. Anand, U. V. Waghmare, K. Biswas, Chem. Mater. 2015, 27,

13 Thermal conductivity of Sn 3 Sn lat (W/mK) 2 1 min T (K) where, V is the unit cell volume, k B is the Boltzman constant and v is the sound velocity (~1800 m/s) for Sn. Pristine Sn exhibits room temperature κ lat value of 2.88 Wm -1 K -1, while theoretical limit for minimum lattice thermal conductivity (κ min ) is ~0.5 Wm -1 K

14 Ultralow thermal conductivity in Sn lat (W/mK) Sn Sn 0.96 Sb 0.04 Sn 0.92 Sb 0.08 Sn 0.88 Sb 0.12 Sn 0.85 Sb 0.15 Sn 0.8 Sb 0.2 min lat (W/mK) Undoped Sn Sn 1-x In x Sn 0.98 Bi x% Hg AgSn x Bi 2+x Sn 1-x Mn x Sn 1.03-x Cd x -2% CdS Sn 0.85 Sb 0.15, present data T (K) Ananya A. Banik, B. Vishal, S. Perumal, R. Datta, K. Biswas, Energy Environ. Sci., 2016, 9,

15 The origin of low thermal conductivity in Sn 1-x Sb x : phonon scattering via layered intergrowth nanostructures Sn-4 % Sb (b) 2-10 nm Sb reach nanoprecipiates in Sn matrix Nanodomains of superstructured intergrowth chalcogenides of Sn m Sb 2n 3n+m in Sn matrix, which scatters heat carrying phonon significantly Sn-15 % Sb [11-1] [1-1-1] [0-20] ZA [101] Superstructure spot A. Banik, B. Vishal, S. Perumal, R. Datta, K. Biswas, Energy Environ. Sci., 2016, 9,

16 Intergrowth chalcogenides: Natural heterostructures Homologues series: M m (Bi/Sb) 2n 3n+m [i.e. (M) m ((Bi/Sb) 2 3 ) n ] M: Ge/Sn/Pb (a) mperature, C (c) PbBi 6 10 PbBi 4 7 L PbBi Bi 2 3 at. % Pb Pb (d) (b) PbBi a c = 1.75 nm Pb 2 Bi Pb 942 C 1.35 nm c Pb 2 Bi 2 5 a c c/3 PbBi 6 10 c a A. Chatterjee and K. Biswas, Angew. Chem. Int. Ed. 2015, 54, 5623

17 zt and mechanical stability zt Sn Sn 0.96 Sb 0.04 Sn 0.92 Sb 0.08 Sn 0.88 Sb 0.12 Sn 0.86 Sb 0.14 Sn 0.85 Sb 0.15 Sn 0.84 Sb 0.16 Sn 0.8 Sb T (K) Microhardness, H v Bi 2 3 Ref. (35) Ref. (36) Pb Ref. (37) Pb 1-x Sn x Ref. (38) PbSe Ref. (39) Cu 2 S Samples This work Ref. (39) Cu 2 Se Sn Sn 0.85 Sb

18 Intrinsic phenomena to suppress lattice thermal conductivity Intrinsic low thermal conductivity is of practical interest due to its robustness against grain size, temperature range and other structural variations. Intrinsically low κ L originating in solids with : (a) complex crystal structures, (b) part-crystalline part-liquid state, (c) rattling modes (d) superionic substructure with liquid-like cation disordering, (e) resonant bonding and (f) anisotropic layered crystal structure,

19 I-V-VI 2 compounds I = Na, Cu, Ag V = Sb, Bi VI = S, Se, Satya NaCl structure Pb Ag/Sb Se Pb AgSbSe 2 Disordered cation sub-lattice - Ag/Sb

20 Synthesis: p-type AgSbSe C Ag + Sb + Se AgSbSe 2 Sealed tube reaction 6 hrs 850 ⁰C 850 ⁰C 4.5 hrs 12 hrs 450 ⁰C Air cooled RT RT Reaction has been done in a vacuum sealed quartz tube. Cut by diamond saw. Polished in presence of water. Ag + (1-x) Sb + x Pb + 2 Se 850 C AgSb 1-x Pb x Se 2 Ag + (1-x) Sb + x Bi + 2 Se 850 C AgSb 1-x Bi x Se 2 Sealed tube reaction X= 2-4 mol % 10 g

21 Ultra-low thermal conductivity 0.8 AgSbSe AgSbSe 2 AgSb 0.98 Bi 0.02 Se 2 AgSb 0.98 Pb 0.02 Se 2 total (W/mK) AgSb 0.96 Bi 0.04 Se 2 total (W/mK) AgSb 0.96 Pb 0.04 Se T (K) T (K) a) High degree of anharmonicity of Sb-Se bonds that gives rise to strong phonon scattering. b) Effective phonon scattering by the highly disordered Ag/Sb lattice. S. N. Guin, A. Chatterjee, D. S. Negi, R. Datta and K. Biswas, Energy Environ. Sci., 2013, 6, 2603

22 Effect of lone pair Ag(Sb/Bi)Se 2 Valence electronic configuration of group V element is ns 2 np 3 Lone pair of electrons can creat strong bond anharmonicity and phonon sacttering, which is reducing the lattice thermal conductivity to the nearly amorphous limit D. T. Morelli, V. Jovovic and J. P. Heremans, Phys Rev. Lett., 2008, 101, The origin of lattice anharmonicity and the ensuing ultralow κ L in the I-V-VI 2 chalcogenides such as AgSbSe 2, AgBiSe 2, AgBiS 2 and AgBiSeS has been traced to the electrostatic repulsion between the stereochemically active ns 2 lone pair of group V cation and the valence p-orbital of group VI anion. S. N. Guin, A. Chatterjee, D. S. Negi, R. Datta and K. Biswas, Energy Environ. Sci., 2013, 6, 2603

23 AgSbSe 2 AgSb 0.98 Bi 0.02 Se 2 AgSb 0.96 Bi 0.04 Se AgSbSe 2 AgSb 0.98 Pb 0.02 Se 2 AgSb 0.96 Pb 0.04 Se ZT % ZT % ZT T (K) T (K) Sample 1 Sample 2 Sample 1 (annealed) T (K)

24 Ultra-low thermal conductivity in In

25 Ultralow Thermal Conductivity in In (In + In 3+ 2 ) (W/mK) In In In T(K) L (W/mK) In In In Theoretical minimum L T(K) Manoj M. K. Jana, K. Pal, U. V. Waghmare, and K. Biswas, Angew. Chem. Int. Ed., 2016, DOI: /anie

26 The Origin of Ultralow Thermal Conductivity in In The structure features coexistent ionic and covalent substructure. The trivalent In 3+ cations form covalent (sp 3 ) In- bonds which construct In tetrahedra. These tetrahedra share the horizontal edges to form covalently bonded anionic substructure with a chain-like topology along the crystallographic z-axis. On the other hand, each monovalent In + cation is surrounded by eight atoms in a distorted square antiprismatic arrangement to form skewed Thompson cubes which forms columnar ionic substructure (In + In 3+ 2 ) Covalently bound substructure y x z 2- In 3+ In 1+ In : I 4/m c m (140) - tetragonal Ionic substructure Anionic chains of corner sharing In tetrahedra (green), bound electrostatically to chains of In + cations (pink) Intrinsic bonding asymmetry M. K. Jana, K. Pal, U. V. Waghmare, and K. Biswas, Angew. Chem. Int. Ed., 2016, DOI: /anie

27 Phonon dispersion of In 0 GPa 3 GPa - 16 cm -1 Rattling vibrations near Γ cm -1 x (d) y z In + In 3+ Displacement of In+ cations along z-direction point, with imaginary frequencies. Off-centering instabilities caused by spherical 5s 2 lone pair of In + Strongly anharmonic with very large Grüneisen values (c) y z x Anti-parallel displacements of In + cations along the (±) z-direction and rotation of In tetrahedra around z-axis These unstable modes involve collective rattling vibrations of In + atoms (// to z-axis) within the columnar ionic substructure.

28 Lone Pair Induced Anharmonic Rattling Potential energy (ev) In 1+ (along x) In 1+ (along z) In 3+ (along x) In 3+ (along z) (along x) (along z) By shifting the atoms away from equilibrium positions (along x- and z-directions), we find that the energy well of off-centered In + atom is very flat unlike In 3+ and 2- atoms which sit in deep potential wells Displacement (Å) x z y x y z U iso 1823(1) 1823(1) 0 17(1) In (1) 2- In 3+ In 1+ U 11 U 22 U 33 In (5) 46(5) 81(3) Fractional coordinates (x10-4 ) and thermal parameters (x10-3 ) Hogg et al, Acta Cryst. 1976, B32, 2689 Large thermal ADPs: rattling In + cations within ionic substructure

29 Lone Pair Induced Anharmonic Rattling Iso-surfaces of total charge density ELF (iso-value of 0.88) covalent bonding within In tetrahedron and isolated In + cations spherical charge density around In + cation due to its s 2 lone electron pair Calculated phonon sound velocities, mode Grüneisen parameters and mode Debye temperatures Direction ν (TA1) (m/s) ν (TA2) (m/s) ν (LA) (m/s) γ(ta1) γ(ta2) γ(la) Θ(TA1) (K) Θ(TA2) (K) Θ(LA) (K) Γ-X Γ-Z Γ-M Average

30 Ultralow Thermal Conductivity in In (W/mK) In In In T(K) L (W/mK) In In In Theoretical minimum L T(K) Intrinsic bonding asymmetry : covalent and ionic substructures leading to phononglass electron-crystal type nature Large ADPs and anharmonic rattling vibrations of In + cations due to weak bonding and lone pair of In +. Anomalously large Gruneisen parameters: strongly anharmonic phonon-phonon interactions M. K. Jana, K. Pal, U. V. Waghmare, and K. Biswas, Angew. Chem. Int. Ed., 2016, DOI: /anie

31 Optimization of power factor and zt via In-deficiencies (S/cm) In In In 2.8x10 19 cm x10 20 cm x10 18 cm T (K) S ( V/K) In In In In In In 0.6 T(K) S 2 ( W/cm-K 2 ) T(K) In In In zt T(K)

32 Conclusions Low thermal conductivity is an attractive paradigm for developing high performance thermoelectric Low thermal conductivity can be achieved by: 1. Phonon scattering through intergrowth nanostructures- Sn-Sb 2. Lone pair induced bond anharmonicity- AgSbSe 2, AgBiSe 2 3. Anharmonic rattling modes/bonding asymmetry- In

33 Acknowledgements Funding support: Department of Science & chnology, India Department of Atomic Energy- BRNS, India Sheiq Saqr Laboratory New chemistry Unit, JNCASR We thank our excellent collaborators: Koushik Pal and Umesh V. Waghmare, JNCASR, Bangalore, India Dirtha Sanyal, VECC-DAE, Kolkata, India Badri Vishal and Ranjan Datta, JNCASR, Bangalore, India Thank you