Main Article Content
La2Ti2-xNbxO7 (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25) powders were synthesised via solid state reaction method, followed by sintering at 1673 K in a reducing atmosphere of 5% H2/N2 gas. The crystal structure, microstructure and thermoelectric (TE) properties of the pure and Nb-doped La2Ti2O7 ceramics were investigated. All compositions were single phase with porous microstructures consistent with their low experimental densities. Thermoelectric results of Nb-doped compositions showed improved properties in comparison to pure La2Ti2O7, suggesting that cation doping has the potential to improve the thermoelectric properties. Generally, the TE results obtained are not suitable for thermoelectric applications. However, the high Seebeck coefficient (≥190 μV/K) and glass-like thermal conductivity ( ≤2.26 w / m.k ) values achieved have opened a new window for exploring the thermoelectric potentials of La2Ti2O7 and other related oxides.
Snyder GJ, Toberer ES. Complex thermoelectric materials. Nat Mater. 2008;7:105–114.
Abanti Nag, Shubha V. Oxide thermoelectric materials: A structure-property relationship. J. Electron. Mater. 2014;43:962–977.
Terry M. Tritt, Subramanian M. Thermoelectric materials, phonomena and applications: A bird’s eye view. MRS Bull. 2006;3:188–198.
Zhiting Tian, Lee S, Chen G. A comprehensive review of heat transfer in thermoelectric materials and devices. Annu. Rev. Heat Transf. 2014;1-64.
Gregor Kieslich, Giacomo Cerretti, Igor Veremchuk, et al. A chemists view: metal oxides with adaptive structures for thermoelectric applications. Phys. Status Solidi Appl. Mater. Sci. 2016;213:808–823.
Jarman T Jarman, Essam E. Khalil, Elsayed Khalaf. Energy analyses of thermoelectric renewable energy sources. Open J. Energy Effic. 2013;2:143–153.
Ichiro Terasaki. Layered cobalt oxides: Correlated electrons for thermoelectrics. in Thermoelectric Nanomaterials: Materials Design and Applications, K. Koumoto and T. Mori, (Eds). Berlin Heidelberg: Springer, Springer Series in Materials Science. 2013;182:51–70.
Ryoji Funahashi, Oxide thernoelectric power generation, in thermolectric applications workshop, San Diego, CA; 2009. Available:https://www.energy.gov/eere/vehicles/2009-thermorlrctrics-applications-workshop-I
Petr Tomeš, Matthias Trottmann, Clemens Suter, et al. Thermoelectric oxide modules (TOMs) for the direct conversion of simulated solar radiation into electrical energy, Materials (Basel). 2010;3:2801–2814.
Terasaki Y, Sasago K. Uchinokura, large thermoelectric power in NaCo2O4 single crystals, Phys. Rev. B. 1997,56:R12685–R12687.
Yuan Jian Zhong, Feridoon azough, robert freer, The effect of La2Ti3O9 second phase on the microstructure and dielectric properties of La2Ti2O7 ceramics, J. Eur. Ceram. Soc. 1995;15:255–263.
Sulgiye Park, Maik Lang, Cameron L Tracy, et al. Response of Gd2Ti2O7 and La2Ti2O7 to swift-heavy ion irradiation and annealing. Acta Mater. 2015;93:1–11.
Jibran Khaliq, Li Chunchun, Chen Kan, et al. Reduced thermal conductivity by nanoscale intergrowths in perovskite like layered structure La2Ti2O7. J. Appl. Phys. 2015;117:2–8.
Zhang N, Li QJ, Huang SG, et al. Dielectric relaxations in multiferroic La2Ti2O7 ceramics. J. Alloys Compd. 2015;652:1–8.
Sadequa J Patwe, Vasundhara Katari, Nilesh P Salke, et al. Structural and electrical properties of layered perovskite type Pr2Ti2O7 : Experimental and theoretical investigations. J. Mater. Chem. 2015;3:4570–4584.
Tanguy Pussacq, Houria Kabbour, Silviu Colis, et al. Reduction of Ln2Ti2O7 layered Perovskites: A survey of the anionic lattice, electronic features, and potentials. Chem. Mater. 2017;29:1047–1057.
Junying Zhang, Wenqiang Dang, Zhimin Ao, et al. Band gap narrowing in nitrogen-doped La2Ti2O7 predicted by density-functional theory calculations. Phys. Chem. Chem. Phys. 2015;17:8994–9000.
Boston R, Schmidt WL, Lewin GD, et al. Protocols for the fabrication, characterization, and optimization of n-type thermoelectric ceramic oxides. Chem. Mater. 2017;29:265–280.
Fawcett TG, Needham F, Crowder C.E, Kabekkodu S. Advanced Materials Analysis using the Powder Diffraction File, in 10th National Conference on x-ray Diffraction and ICDD Workshop. 2009;1–3.
Adindu C Iyasara, Whitney L Schmidt, Rebecca Boston, et al. La and Sm co-doped SrTiO3-δ thermoelectric ceramics. Mater. Today Proc. 2017;4:12360–12367.
Elizabeth J Harvey, Sharon E Ashbrook, Gregory R Lumpkin, Simon AT. Redfern, characterisation of the (Y1−x La x )2Ti2O7 system by powder diffraction and nuclear magnetic resonance methods. J. Mater. Chem. 2006;16:4665–4674.
Chang Sun Park, Min Hee Hong, Hyung Hee Cho, Hyung Ho Park. Effect of mesoporous structure on the Seebeck coefficient and electrical properties of SrTi0.8Nb0.2O3. Appl. Surf. Sci. 2017; 409:17–21.
Min Hee Hong, Chang Sun Park, Sangwoo Shin, et al. Effect of surfactant concentration variation on the thermoelectric properties of mesoporous ZnO. J. Nanomater. 2013;1–6.
Peng Peng Shang, Bo Ping Zhang, Yong Liu, et al. Preparation and thermoelectric properties of la-doped SrTiO3 ceramics. J. Electron. Mater. 2011;40:926–931.
Iqbal Mahmud, Man-Soon Yoon, Il-Ho Kim, et al. Thermoelectric properties of the ceramic oxide Sr1−x LaxTiO3. J. Korean Phys. Soc. 2016;68:35–40.
Sudireddy BR, Agersted K. Sintering and electrical characterization of La and Nb Co-doped SrTiO3 electrode materials for solid oxide cell applications. Fuel Cells. 2014;14:961–965.
Peng Peng Shang, Bo Ping Zhang, Jing Feng Li, Ning Ma. Effect of sintering temperature on thermoelectric properties of La-doped SrTiO3 ceramics prepared by sol-gel process and spark plasma sintering. Solid State Sci. 2010;12:1341–1346.
Venkatasubramanian R, Siivola E, Colpitts T, O’Quinn B. Thin-film thermoelectric devices with high room-temperature figures of merit. Nature. 2001;413:597–602.
Jiao Han, Qiu Sun, Ying Song. Enhanced thermoelectric properties of La and Dy co-doped, Sr-deficient SrTiO3ceramics. J. Alloys Compd. 2017;705:22–27.
Ioffe AF. Semiconductor thermoelements and thermoelectric cooling. Infosearch Ltd; 1957.
Hong Chao Wang, Chun Lei Wang, Wen Bin Su, et al. Doping effect of La and Dy on the thermoelectric properties of SrTiO3. J. Am. Ceram. Soc. 2011;94:838–842.
Jun Wang, Bo Yu Zhang, Hui Jun Kang, et al. Record high thermoelectric performance in bulk SrTiO3 via nano-scale modulation doping. Nano Energy. 2017; 35:387–395.
Wang HC, Wang CL, Su WB, Liu J, et al. Enhancement of thermoelectric figure of merit by doping Dy in La0.1Sr0.9TiO3 ceramic. Mater. Res. Bull. 2010;45:809–812.
Liu J, Wang CL, Li Y, et al. Influence of rare earth doping on thermoelectric properties of SrTiO3 ceramics. J. Appl. Phys. 2013;114.
Sung-Hwan Bae, Jun-Young Cho, O-Jong Kwon, et al. The effect of grain size and density on the thermoelectric properties of Bi2Te3-PbTe compounds. J. Electron. Mater. 2013;42:3390–3396.
Yang Shen, David R Clarke, Paul A Fuierer. Anisotropic thermal conductivity of the Aurivillus phase, bismuth titanate (Bi4Ti3O12): A natural nanostructured superlattice. Appl. Phys. Lett. 2008;93:10–13.
Taylor D Sparks, Paul A Fuierer, David R Clarke. Anisotropic thermal diffusivity and conductivity of La-doped strontium niobate Sr2Nb2O7. J. Am. Ceram. Soc. 2010; 93:1136–1141.
Shingo Ohta, Takashi Nomura, Hiromichi Ohta, Kunihito Koumoto. High-temperature carrier transport and thermoelectric properties of heavily La- or Nb-doped SrTiO3 single crystals. J. Appl. Phys. 2005; 97:0341061-0341064.