. et al. (5 more authors) (2014) A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3. Nature Materials, 13 (1). 31 -35. ISSN 147631 -35. ISSN -1122 https://doi.org/10.1038/NMAT3782 eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Introductory paragraphOxide ion conductors find important technical applications in electrochemical devices such as solid oxide fuel cells (SOFCs), oxygen separation membranes and sensors 1-9 . Na 1/2 Bi 1/2 TiO 3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity which is problematic for its piezoand ferroelectric applications 10-15 . Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~ 0.01 S cm -1 at 600 o C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives [10][11][12][13][14][15] . NBT exhibits maximum relative permittivity,  r ~ 3000 at ~ 320 o C (T max ) and possesses a distorted perovskite structure with extensive chemical, cationdisplacement and octahedral tilt disorder. 14 The resulting complex nanodomain structure is well known to facilitate high and temperature stable permittivity behaviour which is suitable for the fabrication of high temperature ceramic capacitors in addition to easy phase switching under the application of a large electric field which creates large strains suitable for actuator applications [10][11][12][13][14][15] . One drawback of NBT for piezoelectric and capacitor applications, however, is its high leakage conductivity 10,11 . The piezoelectric properties and room temperature dc conductivity depend on the nominal starting composition 10,11 , the origin of which has not been resolved. Here we report on the surprising and dramatic sensitivity of the ionic and electronic transport properties of NBT on low levels of A-site nonstoichiometry in the nominal starting composition. We demonstr...

Introducing controlled electrical homogeneity can be an effective way to obtain ultrahigh energy storage density in lead-free multilayers.

No abstract

Simulations of electron diffraction patterns for each of the known perovskite tilt systems have been performed. The conditions for the appearance of superlattice reflections arising from rotations of the octahedra are modified to take into account the effects of different tilt systems for kinematical diffraction. The use of selected-area electron diffraction as a tool for perovskite structure determination is reviewed and examples are included.

We show that oxy-fluoride glass ceramics, with typical composition, 32(SiO2):9(AlO1.5):31.5(CdF2):18.5(PbF2):5.5(ZnF2): 3.5(ErF3) mol % have potential applications in telecommunications. Upon heat treatment, Er3+ nucleates the growth of the nanocrystalline β-PbF2, which acts as its host. Heat treatment at 440 °C for 5 h and at 390 °C for 3 h gave rise to ∼12 and ∼2.5 nm diameter crystals, respectively. The emission band of Er3+ in the 1.54 μm telecommunications window (4I13/2→4I15/2 transition, at the half-height width) was 75 nm in the former and 90 nm in the latter case, while I13/24↔I15/24 absorption and emission bands became wavelength divergent in both cases. Also in the latter case, the spectrum was flat from 1.53 to 1.56 μm. The evolution of spectral behavior is explained by changes in average site geometry of the Er3+ dopant, related to the α→β phase transition of PbF2, which is stimulated by heat treatment.

Bismuth ferrite-based lead-free multilayers with a high recoverable energy density of 6.74 J cm−3 and an efficiency of 77%, stable up to 125 °C.

No abstract

No abstract