(2017) 'New apatite-type oxide ion conductor, Bi2La8[(GeO4)6]O3 : structure, properties, and direct imaging of low-level interstitial oxygen atoms using aberration-corrected scanning transmission electron microscopy.', Advanced functional materials., 27 (8). p. 1605625.Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The new solid electrolyte Bi2La8[(GeO4)6]O3 has been prepared and characterized by variabletemperature synchrotron X-ray and neutron diffraction, aberration-corrected scanning transmission electron microscopy and physical property measurements (impedance spectroscopy and second harmonic generation). The material is a triclinic variant of the apatite structure type and owes its ionic conductivity to the presence of oxide ion interstitials. A combination of annular bright-field scanning transmission electron microscopy experiments and frozen-phonon multi-slice simulations enabled direct imaging of the crucial interstitial oxygen atoms present at a level of 8 out of 1030 electrons per formula unit of the material, and crystallographically disordered, in the unit cell. Scanning transmission electron microscopy also led to a direct observation of the local departures from the centrosymmetric average structure determined by diffraction. As no second harmonic generation signal was observed, these displacements are non-cooperative on the longer length scales probed by optical methods.2

Ionic-conducting materials are crucial for the function of many advanced devices used in a variety of applications, such as fuel cells and gas separation membranes. Many different chemical controls, such as aliovalent doping, have been attempted to stabilise δ-Bi 2 O 3 , a material with exceptionally high oxide ion conductivity which is unfortunately only stable over a narrow temperature range. In this study, we employ a multinuclear, variable-temperature NMR spectroscopy approach to characterise and measure oxide ionic motion in the V-and P-substituted bismuth oxide materials Bi 0.913 V 0.087 O 1.587 , Bi 0.852 V 0.148 O 1.648 and Bi 0.852 P 0.148 O 1.648 , previously shown to have excellent ionic conduction properties (Kuang et al., Chem. Mater. 2012,

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

Lone-pair cations are known to enhance oxide ion conductivity in fluorite- and Aurivillius-type materials. Among the apatite-type phases, the opposite trend is found for the more widely studied silicate oxide ion conductors, which exhibit a dramatic decrease in conductivity on Bi(iii) incorporation. In this work, the influence of lone-pair cations on the properties of apatite-type germanate oxide ion conductors has been investigated by preparing and characterising seven related compositions with varying Bi(iii) content, by X-ray and neutron powder diffraction and impedance spectroscopy. All materials are very good oxide ion conductors (with conductivities of up to 1.29 × 10 S cm at 775 °C). Increasing Bi(iii) content leads to increases in conductivity by up to an order of magnitude, suggesting significant differences in the oxide-ion conduction mechanisms between lone-pair-containing apatite-type germanate and silicate solid electrolytes.