Enhancement of thermoelectric performance in strontium titanate by praseodymium substitution

Abstract

In order to identify the effects of Pr additions on thermoelectric properties of strontium titanate, crystal structure, electrical and thermal conductivity, and Seebeck coefficient of Sr1−xPrxTiO3 (x = 0.02–0.30) materials were studied at 400 < T < 1180 K under highly reducing atmosphere. The mechanism of electronic transport was found to be similar up to 10% of praseodymium content, where generation of the charge carriers upon substitution resulted in significant increase of the electrical conductivity, moderate decrease in Seebeck coefficient, and general improvement of the power factor. Formation of point defects in the course of substitution led to suppression of the lattice thermal conductivity, whilst the contribution from electronic component was increasing with carrier concentration. Possible formation of layered structures and growing distortion of the perovskite lattice resulted in relatively low thermoelectric performance for Sr0.80Pr0.20TiO3 and Sr0.70Pr0.30TiO3. The maximum dimensionless figure of merit was observed for Sr0.90Pr0.10TiO3 and amounted to ∼0.23 at 670 K and ∼0.34 at 1170 K, close to the values, obtained in similar conditions for the best bulk thermoelectrics, based on rare-earth substituted SrTiO3.

Design of SrTiO3-Based Thermoelectrics by Tungsten Substitution

“…9B,C and confirms the minor effect from the charge carriers on the heat transfer. Although in the case of the substitution of titanium with heavy tungsten one may anticipate significant decrease in κ ph due to mass-difference impurity scattering [33][34][35], the calculated values of the thermal conductivity are only moderately below or similar to those observed for other low-substituted perovskite-type titanates, cited above for PF comparison [16,17,24,62]. Separation of the phase impurities at nanoscale level in SrTi 0.94 W 0.06 O 3±δ , which are likely to act as phonon scattering interfaces, also did not result in any evident lowering of κ ph , though corresponding impact can be hindered by other structural and microstructural effects.…”

“…Ceramics processing in reducing conditions at elevated temperatures is essential for creating an appropriate concentration of the electronic defects in titanates and to achieve reasonable power factor. Attractive values of the thermoelectric figure of merit ZT (σ×α 2 ×T/κ) were observed for reduced (Sr,Ln)TiO 3 (Ln=La, Pr, Nd, Sm, Dy, Y) [15][16][17][18][19][20][21][22][23] and Sr(Ti,Nb)O 3 [9,24,25]. Compared to the diverse number of options for A-site substitution, the set of appropriate cations to substitute in B-site as a donor is, however, limited to niobium, tantalum, molybdenum and tungsten, if one considers reasonable natural abundance and other critical limitations 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 such as toxicity.…”

New insights on the synthesis and electronic transport in bulk polycrystalline Pr-doped SrTiO3−δ

“…9 The possibility of the cubic to tetragonal transition, which has been reported before for SrTiO 3 upon incorporation of Pr with x ! 0.1 (using Pr 6 O 11 ), [17][18][19][20] was also investigated. It is known that the cubic to tetragonal transition can be characterized by monitoring the peak splitting of the {200} reflection.…”

“…Values reported by Kovalevsky et al for Sr 0.95 Pr 0.05 TiO 3 using Pr 6 O 11 as the doping source were also shown for comparison. 20 Similar power factor values and temperature-dependence were achieved in the whole In order to investigate the maximum achievable thermoelectric power factor and the corresponding optimum doping concentration for the samples prepared following our synthesis strategy, the electronic transport coefficients were calculated using the Boltzmann transport equation under the relaxationtime approximation. For a given carrier concentration, n, the Fermi energy, E F , can be determined in a given energy range by self-consistently solving the following equation:…”

Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO3−δ ceramics originating from nonuniform distribution of Pr dopants

“…Reported maximum ZT values in the literature for single-and polycrystalline SrTiO 3 are also shown for comparison. [2][3][4]8,18,19 Pr-doped SrTiO 3 polycrystalline samples prepared using the strategy employed in this work shows much higher ZT values over the whole temperature range under study. Maximum ZT values above 0.6 can be predicted at 1000 C by fitting the experimental electronic and thermal transport data, if the measurements are to be performed under a highly reducing atmosphere.…”