Self-Nanostructuring in SrTiO3: A Novel Strategy for Enhancement of Thermoelectric Response in Oxides

Feridoon Azough, Ali Gholinia, Diana T. Alvarez-Ruiz, Ercin Duran, Demie M. Kepaptsoglou, Alexander S. Eggeman, Quentin M. Ramasse, Robert Freer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

58 Citations (Scopus)

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 Pm3 m 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.

Original languageEnglish
Pages (from-to)32833-32843
Number of pages11
JournalACS applied materials & interfaces
Volume11
Issue number36
DOIs
Publication statusPublished - 11 Sept 2019
Externally publishedYes

Bibliographical note

Publisher Copyright:
Copyright © 2019 American Chemical Society.

Funding

The authors are grateful to the EPSRC for the provision of funding for this work (EP/H043462, EP/I036230/1, EP/L014068/1 EP/L017695/1 acknowledged by R.F.). SuperSTEM is the EPSRC National Research Facility for Advanced Electron Microscopy and is supported by EPSRC. All research data supporting this publication are directly available within the publication. The authors are grateful to the EPSRC for the provision of funding for this work (EP/H043462, EP/I036230/1, EP/L014068/1, EP/L017695/1 acknowledged by R.F.). SuperSTEM is the EPSRC National Research Facility for Advanced Electron Microscopy and is supported by EPSRC. All research data supporting this publication are directly available within the publication.

FundersFunder number
EPSRC National Research Facility for Advanced Electron Microscopy
R.F.
Engineering and Physical Sciences Research CouncilEP/L014068/1, EP/M50774X/1, EP/J000620/1, EP/H043462, EP/L017695/1, EP/I03601X/1, EP/I036230/1

    Keywords

    • 3D electron diffraction
    • aberration corrected microscopy
    • nanostructuring
    • oxide thermoelectric
    • perovskite
    • strontium titanate
    • thermal conductivity

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