BiCuSeO Thermoelectrics: Recent Progress and Perspective Andrei Novitskii Academic Research Center for Energy Efficiency, National University of Science and Technology MISIS, Moscow, Russia

Thermoelectricity BiCuSeO oxyselenides / 22 March 2021 2 ZT is the average for the device over the temperature range Tc to Th . Thus, η depends mainly on the ΔT and materials’ performance: where α is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity. [1] A. Shakouri, Annu. Rev. Mater. Res. 41 (2011) 399–431 [2] D.M. Rowe, CRC Handbook of Thermoelectrics: Macro to Nano, CRC Press, 2006 [3] G.J. Snyder, E.S. Toberer, Nat. Mater. 7 (2008) 105–114 Thermoelectrics 1 1 , 1 c h c h h Carnotcycle Т Т ZT Т ZT Т Т  − + − = + + Th Tc 2 zT T    =

BiCuSeO oxyselenides: Background BiCuSeO oxyselenides / 22 March 2021 3 [4] V. Johnson, W. Jeitschko, J. Solid State Chem. 11 (1974) 161–166. [5] M. Palazzi, C. Carcaly, J. Flahaut, J. Solid State Chem. 35 (1980) 150–155. [6] M. Palazzi, S. Jaulmes, Acta Crystallogr. Sect. B Struct. Crystallogr. Cryst. Chem. 37 (1981) 1337–1339. [7] L.N. Kholodkovskaya, L.G. Akselrud, A.M. Kusainova, V.A. Dolgikh, B.A. Popovkin, Mater. Sci. Forum 133–136 (1993) 693–696. [8] A.M. Kusainova, P.S. Berdonosov, L.G. Akselrud, L.N. Kholodkovskaya, V.A. Dolgikh, B.A. Popovkin, J. Solid State Chem. 112 (1994) 189–191. [9] R. Pöttgen, D. Johrendt, Zeitschrift Fur Naturforsch. - Sect. B J. Chem. Sci. 63 (2008) 1135–1148. • Quaternary ZrCuSiAs and HfCuSiAs silicidoarsenides were firstly synthesized in 1974 by V. Johnson and W. Jeitschko [4]; • R3+T+S2-O2- oxysulfides (R – rare-earth elements, T – transition metals) were synthesized in 1980. They crystallize in the same ZrCuSiAs structural type and have been studied as promising oxide materials for solar cells with attractive optical properties and ionic conductivity [5,6]; • Oxychalcogenides Ln3+Cu+Ch2-O2- (Ln – Bi or lanthanides, Ch - chalcogenide) were synthesized at Moscow State University and Lviv State University in 1993. Only structural studies [7,8]; • 1990’s – R3+T2+Pn3-O2- oxypnictides (Pn – pnictide [nitrogen subgroup]) as potential high-Tc superconductors (but no superconductivity) [9];

BiCuSeO oxyselenides: Background BiCuSeO oxyselenides / 22 March 2021 4 [10] T. Ohtani, Y. Tachibana, Y. Fujii, J. Alloys Compd. 262–263 (1997) 175–179. [11] H. Hiramatsu, H. Yanagi, T. Kamiya, K. Ueda, Chem. Mater. 20 (2008) 326–334. [12] L.D. Zhao, D. Berardan, Y.L. Pei, C. Byl, L. Pinsard-Gaudart, N. Dragoe, Appl. Phys. Lett. 97 (2010) 092118. [13] Y. Liu, L.-D. Zhao, Y. Zhu, Y. Liu, F. Li, M. Yu, D.-B. Liu, W. Xu, Y.-H. Lin, C.-W. Nan, Adv. Energy Mater. 6 (2016) 1502423. • First study on electrical transport properties of BiCuSeO with Sr doping at Bi site and Cu vacancy formation in 1997 [10]; • In early 2000’s oxychalcogenides RCuChO were studied as widegap transparent p-type semiconductors, ‘‘natural multiple quantum wells’ concept; • Late 2000’s – superconductivity in RFePnO at low temperature (< 55 K); • It was firstly shown in 2008 that BiCuChO exhibits much lower bandgap of 0.5- 1.1 eV that that for RCuChO (2.5-3.2 eV) [11]; • Firstly reported zT value for Sr-doped BiCuSeO by the Nita Dragoe group in 2010 [12]; The beginning of active research on BiCuSeO as promising thermoelectric materials; • The highest zTmax value of ~1.5 achieved in dually doped BiCuSeO with Ca and Pb at Bi site [13].

Overview BiCuSeO oxyselenides / 22 March 2021 5 [13] Y. Liu, L.-D. Zhao, Y. Zhu, Y. Liu, F. Li, M. Yu, D.-B. Liu, W. Xu, Y.-H. Lin, C.-W. Nan, Adv. Energy Mater. 6 (2016) 1502423. [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727. O Se Cu Bi [Cu+ 2 Se2- 2 ]2- conducting layer [Bi3+ 2 O2- 2 ]2+ insulating layer BiCuSeO: • Layered structure; • Intrinsically low thermal conductivity; • Moderate electrical transport; • p-type conductivity; • High thermal stability up to 923 K; • Eg ~0.8 eV; • zTmax ~1.5 at 823 K

zT enhancement strategies BiCuSeO oxyselenides / 22 March 2021 6 charge carrier optimization band structure engineering defect engineering … synthesis method optimization new synthesis techniques texturation …

Charge carrier optimization. Doping at Bi site BiCuSeO oxyselenides / 22 March 2021 7 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Band engineering BiCuSeO oxyselenides / 22 March 2021 8 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Band engineering BiCuSeO oxyselenides / 22 March 2021 9 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Dual doping or MD BiCuSeO oxyselenides / 22 March 2021 10 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Dual doping or MD BiCuSeO oxyselenides / 22 March 2021 11 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Dual doping or MD BiCuSeO oxyselenides / 22 March 2021 12 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Defect engineering BiCuSeO oxyselenides / 22 March 2021 13 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Summary BiCuSeO oxyselenides / 22 March 2021 14 Simple carrier counting: [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727. ( ) 2 1 2 1 2(1 ) 2 2 2 2 2(Bi CuSeO) (Bi O ) (Cu Se ) 2 x x x x x M M xh − + − • − − = + + ( ) ( ) 2 1 2 ' 1 2 2 2 2 1 2(BiCu SeO) (Bi O ) (Cu Se ) 2 2 Cu V h      + − + • − − = + + + Eform (VCu ) ~ 0 eV

Charge carrier optimization. Summary BiCuSeO oxyselenides / 22 March 2021 15 • Band structure engineering • Charge carrier optimization • Dual doping • Deficiency introduction • Modulation doping • Structure modification (fabrication techniques) • Texturation • Mechanical alloying • Reactive SPS • Self-propagating high- temperature synthesis • Composites • Nanoinclusions … [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Summary BiCuSeO oxyselenides / 22 March 2021 16 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727.

Charge carrier optimization. Summary BiCuSeO oxyselenides / 22 March 2021 17 [14] A. Novitskii, T. Mori, Preprint (2020) DOI: 10.13140/RG.2.2.15661.10727. This data is available at Mendeley Data: DOI 10.17632/7vhgd5cwmc.1

Methods. Traditional synthesis route BiCuSeO oxyselenides / 22 March 2021 18 raw powders mixing, cold-pressing solid state reaction in quartz tube SPS BiCuSeO disc-shaped bulk samples in 40 – 70 hours ball milling & cold- pressing ball milling or hand grinding − Not industrially friendly; − Cumbersome; − Energy intensive; − Time consuming.

Methods. Self-propagating high-temperature synthesis BiCuSeO oxyselenides / 22 March 2021 19 raw powders mixing, cold-pressing SPS BiCuSeO bulk samples in 1 – 2 hours ball milling or grinding [19] G.-K. Ren, J.-L. Lan, S. Butt, K.J. Ventura, Y.-H. Lin, C.-W. Nan, RSC Adv. 5 (2015) 69878–69885.

BiCuSeO bulk samples in 1 – 8 hours BiCuSeO oxyselenides / 22 March 2021 20 raw powders ball milling SPS [20] J. Wu, F. Li, T.-R. Wei, Z. Ge, F. Kang, J. He, J.-F. Li, J. Am. Ceram. Soc. 99 (2016) 507–514. Methods. Mechanochemical synthesis

BiCuSeO bulk samples in 1 – 8 hours BiCuSeO oxyselenides / 22 March 2021 21 raw powders ball milling SPS [20] J. Wu, F. Li, T.-R. Wei, Z. Ge, F. Kang, J. He, J.-F. Li, J. Am. Ceram. Soc. 99 (2016) 507–514. Methods. Mechanochemical synthesis

BiCuSeO bulk samples in 1 – 2 hours BiCuSeO oxyselenides / 22 March 2021 22 raw powders ball milling RSPS [21] A. Novitskii, G. Guélou, A. Voronin, T. Mori, V. Khovaylo, Scr. Mater. 187 (2020) 317–322. Methods. Reactive SPS Bi2 O3 + Bi + 3Cu + 3Se → 3BiCuSeO Bi + Se + CuO → BiCuSeO ΔG°1 ΔG°2 ΔG°1 > ΔG°2

Methods. Summary BiCuSeO oxyselenides / 22 March 2021 23

Conclusions & outlook BiCuSeO oxyselenides / 22 March 2021 24 Main advantages: • One of the best p-type Pb-free polycrystalline thermoelectric with zTmax = 1.4 at 923 K and zTav = 1.1 between 623 - 923 K; • It is possible to synthesize BiCuSeO via scalable powder metallurgy methods; Main trends: • Double doping combining various approaches Still much work to do: • Find suitable n-type material, Bi2 O2 Se? • Contact and diffusion barrier layers? • Mechanical properties?

Acknowledgements BiCuSeO oxyselenides / 22 March 2021 25 The study was carried out with financial support from the Russian Science Foundation (project no. 19-79-10282). @anovitzkij @energy_misis novitskiy@misis.ru

BiCuSeO oxyselenides / 22 March 2021 Thank you for your attention The study was carried out with financial support from the Russian Science Foundation (project no. 19-79-10282). @anovitzkij @energy_misis novitskiy@misis.ru