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Azough F, Gholinia A, Alvarez-Ruiz DT, Duran E, Kepaptsoglou DM, Eggeman AS, Ramasse QM, Freer R. Self-Nanostructuring in SrTiO 3: A Novel Strategy for Enhancement of Thermoelectric Response in Oxides. ACS Appl Mater Interfaces 2019; 11:32833-32843. [PMID: 31419381 DOI: 10.1021/acsami.9b06483] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nanostructuring is recognized as an efficient route for enhancing thermoelectric response. Here, we report a new synthesis strategy for nanostructuring oxide ceramics and demonstrate its effectiveness on an important n-type thermoelectric SrTiO3. Ceramics of Sr0.9La0.1TiO3 with additions of B2O3 were synthesized by the mixed oxide route. Samples were sintered in air followed by annealing in a reducing atmosphere. Crystallographic data from X-ray and electron diffraction showed Pm3̅m cubic symmetry for all the samples. High-resolution transmission electron microscopy (HRTEM) showed the formation of a core-shell type structure within the grains for the annealed ceramics. The cores contain nanosize features comprising pairs of nanosize voids and particles; the feature sizes depend on annealing time. Atomic-resolution, high-angle annular-dark-field imaging and electron energy loss spectroscopy in the scanning transmission electron microscopy (STEM-HAADF-EELS) showed the particles to be rich in Ti and the areas around the voids to contain high concentrations of Ti3+. Additionally, dislocations were observed, with significantly higher densities in the shell areas. The observed dislocations are combined (100) and (110) edge dislocations. The major impact of the core-shell type microstructures, with nanosize inclusions, is the reduction of the thermal conductivity. Sr0.9La0.1TiO3 ceramics containing grain boundary shells of size ≈ 1 μm and inclusions in the core of 60-80 nm exhibit a peak power factor of 1600 μW/m·K2 at 540 K; at 1000 K, they exhibit a low thermal conductivity (2.75 W/m·K) and a power factor of 1050 μW/m·K2 leading to a high of ZT of 0.39 ± 0.03. This is the highest ZT reported so far for Sr0.9La0.1TiO3 based-compositions. This nanostructuring strategy should be readily applicable to other functional oxides.
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Affiliation(s)
- Feridoon Azough
- School of Materials , University of Manchester , Manchester , M13 9PL , U.K
| | - Ali Gholinia
- School of Materials , University of Manchester , Manchester , M13 9PL , U.K
| | | | - Ercin Duran
- School of Materials , University of Manchester , Manchester , M13 9PL , U.K
| | - Demie M Kepaptsoglou
- SuperSTEM Laboratory , STFC Daresbury Campus , Daresbury WA4 4AD , U.K
- Jeol Nanocentre and Department of Physics , University of York , Heslington, York YO10 5DD , U.K
| | | | - Quentin M Ramasse
- SuperSTEM Laboratory , STFC Daresbury Campus , Daresbury WA4 4AD , U.K
- School of Chemical and Process Engineering and School of Physics , University of Leeds , Leeds LS2 9JT , U.K
| | - Robert Freer
- School of Materials , University of Manchester , Manchester , M13 9PL , U.K
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