Electronic transport properties of Sr1−<i>x</i>La<i>x</i>TiO3 ceramics

Moos, Ralf; Härdtl, Karl Heinz

doi:10.1063/1.362796

Cited by 214 publications

(103 citation statements)

References 22 publications

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“…S9, ESI †). 35 Above this temperature, σ decreases with increasing T as carrier mobility is reduced with a σ for La0.5Na0.5Ti0.8Nb0.2O3 comparable to that of Sr0.9Dy0.1TiO3-δ measured in this study. Observation of negative thermopowers indicates that the carriers are predominantly n-type in nature, and the absolute magnitudes of S500 K decrease from -22211 to -1276 μV K -1 from x = 0.05 to 0.2 as a result of increasing carrier concentration n (Fig.…”

Section: J Namementioning

confidence: 67%

Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

Daniels

Саввин

Pitcher

et al. 2017

Energy Environ. Sci.

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a Phonon-glass electron-crystal (PGEC) behaviour is realised in La0.5Na0.5Ti1-xNbxO3 thermoelectric oxides. The vibrational disorder imposed by the presence of both La 3+ and Na + cations on the A site of the ABO3 perovskite oxide La0.5Na0.5TiO3 produces a phonon-glass with a thermal conductivity, κ, 80% lower than that of SrTiO3 at room temperature. Unlike other state-of-the-art thermoelectric oxides, where there is strong coupling of κ to the electronic power factor, the electronic transport of these materials can be optimised independently of the thermal transport through cation substitution at the octahedral B site. The low κ of the phonon-glass parent is retained across the La0.5Na0.5Ti1-xNbxO3 series without disrupting the electronic conductivity, affording PGEC behaviour in oxides.Thermoelectric generators offer enhanced energy efficiency across the industrial and automotive sectors through the conversion of waste heat into electricity. Materials performance is assessed by the dimensionless figure of merit ZT = (S 2 σ/κ)T, combining the thermal conductivity (κ), absolute temperature (T), the Seebeck coefficient (S) and electrical conductivity (σ), which together define the power factor (S 2 σ). One strategy to optimise ZT is the phononglass electron-crystal (PGEC) concept proposed by Slack, 1 which aims to decouple the quantities governed by the Boltzmann transport equation in an "electron-crystal", by maximising S and σ, from the quantity governed by phonon transport processes in a "phonon-glass" (PG) by minimising the lattice contribution to the thermal conductivity (κlatt); essentially, a crystal that transports charge like a semiconductor, whilst hindering the transport of heat by the lattice like a glass. 2 Heat transport in solids consists of lattice and electronic (κelec) contributions through κ = κlatt + κelec, and κlatt=1/3Cv·lph·νs (Equation 1), where Cv is the isochoric heat capacity, lph the average phonon mean free path (MFP), and vs the mean velocity of sound. Different heat-carrying mechanisms lead to a broad distribution of MFPs, ranging from the atomic scale (<1 nm) for point defect scattering, to the mesoscale (>100 nm) for grain boundary scattering. In a "phonon-crystal" (PC), heat is transported by phonons of well-defined wavelength. The phonon scattering rate (ph -1 ), which is inversely proportional to κlatt (Equation S1, ESI †), corresponds to the sum of the inverse relaxation times of several phonon-scattering mechanisms that contribute separately to κ and is described quantitatively by the modified Debye-Callaway model (Equation S3, ESI †). 3 This produces a T -1 temperature dependence of κ above the Debye temperature (D) where heat conduction is by Oxide materials are of current interest as high-temperature energy-harvesting thermoelectrics in the automotive and manufacturing sectors due to their low cost, low toxicity and high chemical robustness. The phonon-glass electron crystal (PGEC) concept which has been successfully used to optimise the thermoelectric figure of merit (Z...

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Section: J Namementioning

confidence: 67%

Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

Daniels

Саввин

Pitcher

et al. 2017

Energy Environ. Sci.

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“…The power law exponent reported in the literature varies from 1.5-2.7 over a temperature range of 100-1300 K. Tufte et al 25 reported an exponent of 2.7 around 100-400 K. Uematsu et al 26 observed an exponent of 2.0 over a temperature range of 500-1000 K. Moos et al 27 noted a change in the exponent from 2.7 close to room tem- perature to 1.6 above 1000 K. Unlike these observations, Ohta et al 7 reported an exponent of 1.5 over 300-1000 K and correlated the behavior to phonon scattering as observed in classical semiconductors 28 . Previous studies found no dependence of the exponent on the carrier concentration.…”

Section: Galvanomagnetic Propertiesmentioning

confidence: 96%

High-temperature thermoelectric response of double-dopedSrTiO3epitaxial films

Ravichandran

Siemons

et al. 2010

Phys. Rev. B

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SrTiO3 is a promising n-type oxide semiconductor for thermoelectric energy conversion. Epitaxial thin films of SrTiO3 doped with both La and oxygen vacancies have been synthesized by pulsed laser deposition (PLD). The thermoelectric and galvanomagnetic properties of these films have been characterized at temperatures ranging from 300 K to 900 K and are typical of a doped semiconductor. Thermopower values of double-doped films are comparable to previous studies of La doped single crystals at similar carrier concentrations. The highest thermoelectric figure of merit (ZT ) was measured to be 0.28 at 873 K at a carrier concentration of 2.5 × 10 21 cm −3 .

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“…The power of ÀM is intermediate to the reported values: À2:7 to À3:2 at 100-300 K and À1:6 at high temperature. 21,22) Figure 7 shows the temperature dependencies on the thermal conductivity of CSed SLTO. The thermal conductivity decreased with the increasing temperature; this was caused by the decrease in the thermal diffusivity.…”

Section: Dependences Of Temperature and Doping Amount Onmentioning

confidence: 99%

Thermoelectric Properties of Combustion-Synthesized Lanthanum-Doped Strontium Titanate

et al. 2007

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The possibility of combustion synthesis of perovskite-oxide thermoelectric materials with the attendant saving of energy and time and without deterioration in the thermoelectric properties was investigated by evaluating the thermoelectric properties of lanthanum-doped strontium titanate (Sr 1Àx La x TiO 3 , 0 x 0:1). The materials were successfully combustion synthesized and spark plasma sintered with 98.0-99.6% of true density, and their thermoelectric properties were evaluated from room temperature to 850 K. The optimal lanthanum doping amount ratio x in the considered temperature range was from 0.06 to 0.08, in which Sr 0:92 La 0:08 TiO 3 sample showed the maximum ZT of 0.22 at 800 K. This value was close to the highest recorded ZT at the same temperature up to now, and the ZT of most samples are higher than those synthesized by the conventional solid state reaction method. Thus, combustion synthesis is promising for producing perovskite-oxide thermoelectric materials for high-temperature application.

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Electronic transport properties of Sr1−xLaxTiO3 ceramics

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Cited by 214 publications

References 22 publications

Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

High-temperature thermoelectric response of double-dopedSrTiO3epitaxial films

Thermoelectric Properties of Combustion-Synthesized Lanthanum-Doped Strontium Titanate

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