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▼ [15a-E206-11] Effective power factor of Sr(Ti,Nb)O3/SrTiO3 superlattices
Keywords:thermoelectric, strontium titanate, superlattice
Electron doped SrTiO3 and its superlattices have attracted attention as oxide based thermoelectric material [1]. Room temperature power factor (PF=S2σ) of electron doped SrTiO3 (bulk) is ~2.5 mW m-1 K-2 in the optimized composition [2], which is comparable to that of Bi2Te3 (~4 mW m-1 K-2). Since thermal conductivity (κ) of SrTiO3 bulk single crystal is quite high (~12 W m-1 K-1), the ZT (S2σTκ-1) is only ~0.06 at room temperature. Recently, significant reduction of thermal conductivity for SrTiO3 based superlattices (SrTiO3/BaTiO3 or SrTiO3/CaTiO3) in the cross-plane direction was reported by Ravichandran et al.; The κ values were ~3 W m-1 K-1 [3], roughly 1/4 of bulk, suggesting effective ZT of SrTiO3 based superlattice would exceed 0.24 at room temperature. Thus, ZT of SrTiO3 based superlattice can reach practical level if the PF can be significantly enhanced.
Here we report ‘effective PF’ of Sr(Ti,Nb)O3/SrTiO3 superlattices exceeds 5 mW m-1 K-2 at room temperature, which is ~200% of corresponding bulk electron doped SrTiO3. Figure shows carrier concentration (effective) dependence of PF for the Sr(Ti,Nb)O3/SrTiO3 superlattices at room temperature. The PF value of x=0.6 exceeds 5 mW m-1 K-2, which is ~200% of that of corresponding bulk. We expected that our SrTiO3 superlattices should exhibit much lower κ (~3 W m-1 K-1 [4]) than that of SrTiO3 bulk, ZT value of the 1 u.c. SrTi0.4Nb0.6O3|~10 u.c. SrTiO3 superlattice may be reached 0.5 at room temperature, which is 800% of bulk SrTiO3.
References
[1] H. Ohta, Mater. Today
[2] H. Ohta et al., Inorg. Chem. 47, 8429 (2008).
[3] J. Ravichandran et al., Nature Mater. 13, 168 (2014)
[4] Y. Zhang and H. Ohta, unpublished
Acknowledgements
This works was supported by Grant-in-Aid for Scientific Research on Innovative Areas (25106007) and Grant-in-Aid for Scientific Research A (25246023) from JSPS.
Here we report ‘effective PF’ of Sr(Ti,Nb)O3/SrTiO3 superlattices exceeds 5 mW m-1 K-2 at room temperature, which is ~200% of corresponding bulk electron doped SrTiO3. Figure shows carrier concentration (effective) dependence of PF for the Sr(Ti,Nb)O3/SrTiO3 superlattices at room temperature. The PF value of x=0.6 exceeds 5 mW m-1 K-2, which is ~200% of that of corresponding bulk. We expected that our SrTiO3 superlattices should exhibit much lower κ (~3 W m-1 K-1 [4]) than that of SrTiO3 bulk, ZT value of the 1 u.c. SrTi0.4Nb0.6O3|~10 u.c. SrTiO3 superlattice may be reached 0.5 at room temperature, which is 800% of bulk SrTiO3.
References
[1] H. Ohta, Mater. Today
[2] H. Ohta et al., Inorg. Chem. 47, 8429 (2008).
[3] J. Ravichandran et al., Nature Mater. 13, 168 (2014)
[4] Y. Zhang and H. Ohta, unpublished
Acknowledgements
This works was supported by Grant-in-Aid for Scientific Research on Innovative Areas (25106007) and Grant-in-Aid for Scientific Research A (25246023) from JSPS.