Crystal structure and proton conductivity of BaSn<sub>0.6</sub>Sc<sub>0.4</sub>O<sub>3-δ</sub>: insights from neutron powder diffraction and solid-state NMR spectroscopy



Kinyanjui, Francis G, Norberg, Stefan T, Knee, Christopher S, Ahmed, Istaq, Hull, Stephen, Buannic, Lucienne, Hung, Ivan, Gan, Zhehong, Blanc, Frederic ORCID: 0000-0001-9171-1454, Grey, Clare P
et al (show 1 more authors) (2016) Crystal structure and proton conductivity of BaSn<sub>0.6</sub>Sc<sub>0.4</sub>O<sub>3-δ</sub>: insights from neutron powder diffraction and solid-state NMR spectroscopy. JOURNAL OF MATERIALS CHEMISTRY A, 4 (14). pp. 5088-5101.

[img] Text
c5ta09744d.pdf - Published version

Download (1MB)

Abstract

The solid-state synthesis and structural characterisation of perovskite BaSn<sub>1-<i>x</i></sub> Sc <sub><i>x</i></sub> O<sub>3-<i>δ</i></sub> (<i>x</i> = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group <i>Pm</i>3<i>m</i>) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. <sup>119</sup>Sn and <sup>45</sup>Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D<sub>2</sub>O. It also indicates that the Sn<sup>4+</sup> and Sc<sup>3+</sup> local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (<i>x</i> ≤ 0.2) and in the tin coordination shell at high concentrations (<i>x</i> ≥ 0.3). <sup>17</sup>O NMR spectra on <sup>17</sup>O enriched BaSn<sub>1-<i>x</i></sub> Sc <sub><i>x</i></sub> O<sub>3-<i>δ</i></sub> materials show the existence of Sn-O-Sn, Sn-O-Sc and Sc-O-Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn<sub>0.6</sub>Sc<sub>0.4</sub>O<sub>3-<i>δ</i></sub> refines the deuteron position at the 24k crystallographic site (<i>x</i>, <i>y</i>, 0) with <i>x</i> = 0.579(3) and <i>y</i> = 0.217(3) which leads to an O-D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10<sup>-4</sup> to 1.1 × 10<sup>-3</sup> S cm<sup>-1</sup> between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature.

Item Type: Article
Depositing User: Symplectic Admin
Date Deposited: 20 Sep 2016 15:26
Last Modified: 05 Oct 2023 09:26
DOI: 10.1039/c5ta09744d
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3003396