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Enhancing the thermoelectric properties of Sr1- xPr2 x/3? x/3TiO3± ? through control of crystal structure and microstructure.

ABSTRACT: A-site deficient perovskites are among the most important n-type thermoelectric oxides. Ceramics of Sr1- xPr2 x/3? x/3TiO3 ( x?=?0.1-1.0) were prepared by solid-state reaction at 1700-1723?K using highly reducing atmospheres. Samples with the highest Sr content had a cubic crystal structure [Formula: see text]; incorporating Pr with A-site vacancies led to a reduction in symmetry to tetragonal ( I4/mcm) and then orthorhombic ( Cmmm) crystal structures. HRTEM showed Pr2/3TiO3 had a layered structure with alternating fully and partially occupied A-sites and a short-range order along the (100) direction. Electrical conductivity was highest in samples of high symmetry ( x???0.40), where the microstructures featured core-shell and domain structures. This enabled a very high power factor of approximately 1.75?×?10-3?W?m-1?K-2 at 425?K. By contrast, at high Pr content, structural distortion led to reduced electron transport; enhanced phonon scattering (from mass contrast, local strain and cation-vacancy ordering) led to reduced, glass-like, thermal conductivity. Carbon burial sintering increased the oxygen deficiency leading to increased carrier concentration, a maximum power factor of approximately 1.80?×?10-3?W?m-1?K-2 at 350?K and thermoelectric figure of merit of 0.26 at 865?K. The paper demonstrates the importance of controlling both crystal structure and microstructure to enhance thermoelectric performance. This article is part of a discussion meeting issue 'Energy materials for a low carbon future'.

SUBMITTER: Ekren D

PROVIDER: S-EPMC6635635 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Enhancing the thermoelectric properties of Sr1- xPr2 x/3□ x/3TiO3± δ through control of crystal structure and microstructure.

Ekren Dursun D Azough Feridoon F Freer Robert R

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 20190708 2152

A-site deficient perovskites are among the most important n-type thermoelectric oxides. Ceramics of Sr1- xPr2 x/3□ x/3TiO3 ( x = 0.1-1.0) were prepared by solid-state reaction at 1700-1723 K using highly reducing atmospheres. Samples with the highest Sr content had a cubic crystal structure [Formula: see text]; incorporating Pr with A-site vacancies led to a reduction in symmetry to tetragonal ( I4/mcm) and then orthorhombic ( Cmmm) crystal ...[more]

PMID: 31280721

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Project description:Pure and modified mesoporous TiO2 nanoparticles with different loadings of NiO (3-20.0 wt %) were prepared through the surfactant-assisted sol-gel approach with the use of cetyltrimethylammonium bromide as a template. The optical and structural properties of different samples were examined using N2 adsorption-desorption analysis, energy-dispersive spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence (PL) spectroscopy. X-ray diffraction results confirmed the insertion of Ni2+ into the lattice of TiO2, and the crystallite size reduced remarkably after the addition of NiO. The diffuse reflectance spectroscopy spectra displayed obvious red shift in the absorption edges, and new absorption bands appeared in the visible region when NiO was added, which indicates the formation of surface defects and oxygen vacancies. The optical band gap of TiO2 reduced sharply when the contents of NiO were increased. The increase in the surface defects as well as oxygen vacancies were examined using PL spectroscopy. The photocatalytic performance of the as-synthesized samples was investigated over photodegradation of brilliant green (BG) and phenol and hydrogen generation under visible light. 10% NiO/TiO2 exhibited the highest photocatalytic efficiency. The photocatalytic activity was improved due to the creation of a p-n junction at the interface of NiO/TiO2, which efficiently promotes the separation of photogenerated electron/hole pairs and consequently enhances its photodegradation activity. According to the photocatalytic activity results, NiO contents were considered one of the most important factors affecting the photodegradation of BG and phenol and H2 evolution. Also, we discussed the mechanism of photodegradation, mineralization (total organic carbon), and photocatalytic reaction kinetics of BG and phenol.

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Enhancing the thermoelectric properties of Sr1- xPr2 x/3? x/3TiO3± ? through control of crystal structure and microstructure.

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Enhancing the thermoelectric properties of Sr<sub>1- x</sub>Pr<sub>2 x/3</sub>□ <sub>x</sub><sub>/3</sub>TiO<sub>3± δ</sub> through control of crystal structure and microstructure.

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