Electron Sandwich Doubles the Thermoelectric Power Factor of SrTiO₃

Abstract

Thermoelectric materials convert a temperature difference into electricity through a phenomenon known as the Seebeck effect, and their efficiency is determined by the dimensionless figure of merit, ZT (≡ S2 · σ · κ−1). Currently, most materials exhibiting high ZT values (ZT > 1) are based on heavy metal compounds, but these materials have low thermal/chemical stability. In this regard, conducting metal oxides attract much attention for thermoelectric power generations at high temperatures based on their advantages in thermal stability over heavy metal compounds. However, the thermoelectric performance of metal oxides is usually low. Here the authors review that an enhanced two‐dimensionality is efficient for enhancing the thermoelectric power factor of metal oxides. The authors fabricate SrTiO3‐based superlattices of [N unit cell SrTi1−xNbxO3|11 unit cell SrTiO3]10, of which the de Broglie wavelengths can be tuned by the substitution of Nb. The maximum power factor of the superlattice composed of the long de Broglie wavelength SrTi1−xNbxO3 exceeds ≈5 mW m−1 K−2, which doubles the value observed from the optimized bulk SrTi1−xNbxO3. This finding can help to reduce the amount of wasted heat and thus wasted fossil fuel in daily activities and industrial factories.

Low thermal conductivity of SrTiO3−LaTiO3 and SrTiO3−SrNbO3 thermoelectric oxide solid solutions

“…Thermoelectric materials, which convert temperature difference into electricity, have attracted increasing attention in energy harvesting technologies 1‐5 . The efficiency of thermoelectric conversion is characterized by the figure of merit, ZT = S 2 · σ · T · κ −1 , where Z is the figure of merit, T is the absolute temperature, S is the thermopower (≡Seebeck coefficient), σ is the electrical conductivity, and κ is the thermal conductivity.…”

Optical Plasmon Excitation in Transparent Conducting SrNbO3 and SrVO3 Thin Films

“…Available data does not allow to gain further insight into the microscopic nature of plasmon damping mechanisms. However, it turns out that the electron scattering time t ee of SNO, deduced from the measured conductivity and the carrier density, is within a similar range (t ee ≈ 1.4-4.6 × 10 −15 s), depending on the actual effective mass (m* ≈ 1.5 m 0 , as deduced from the corresponding plasma frequency; m* ≈ 0.46 m 0 [19,20] from Seebeck coefficient or DFT) used for calculations. A similar agreement has been reported in Au.…”

“…Summary of calculations of the scattering rate in SNO and SVO films. The effective mass m* was either taken from SNO [19,20] and SVO [22][23][24] references, or from the our ellipsometry data (together with dc transport data). The relative permittivity value (ε r = 4) used to calculate the m* from ellipsometric data was taken from Makino et al [24] and is estimated to be nearly identical for SVO and SNO.…”

“…The commonly used expressions are valid for simple parabolic electronic bands and allow comparison between data reported by different authors on related materials. [6,8,[10][11][12]19,20,22,24,37] However, in nd 1 -t 2g (n = 1, 2) metals such as SVO and SNO, the conduction bands (mainly xy, xz, and yz) have different dispersion and thus reducing the effective mass to a single value should only be taken as a working approximation.…”

Harvesting Thermal Energy through Pyroelectric and Thermoelectric Nanomaterials for Catalytic Applications

“…With proper doping, these materials can be turned into TE materials. For example, it has been found that Nb/La-doped SrTiO 3 shows very high S due to the heavy effective mass of Ti 3d orbital [71][72][73]. Adopting these materials can simultaneously fulfill high S and suitable band structure, bringing enhanced performance.…”