Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

On the Arrangement of Pentagonal Columns in Tetragonal Tungsten Bronze-Type Nb18W16O93

Version 1 : Received: 11 November 2021 / Approved: 12 November 2021 / Online: 12 November 2021 (15:17:48 CET)

A peer-reviewed article of this Preprint also exists.

Krumeich, F. On the Arrangement of Pentagonal Columns in Tetragonal Tungsten Bronze-Type Nb18W16O93. Crystals 2021, 11, 1514. Krumeich, F. On the Arrangement of Pentagonal Columns in Tetragonal Tungsten Bronze-Type Nb18W16O93. Crystals 2021, 11, 1514.

Journal reference: Crystals 2021, 11, 1514
DOI: 10.3390/cryst11121514

Abstract

The evaluation of HAADF-STEM images of a sample with the composition Nb18W16O93 provided new insights in its real structure. The basic structure comprises an intact octahedral framework of the tetragonal tungsten bronze (TTB) type. The partial occupation of the pentagonal tunnels (PT) by metal-oxygen strings determines the oxygen to metal ratio (O/SM with M = Nb,W). For a large area, the O/SM was determined to be 2.755 which is smaller than the value of Nb18W16O93 which is O/SM = 2. 735. To a large extent, the threefold TTB superstructure structure of Nb8W9O47 with a high oxygen content is present (O/SM = 2.765). In addition, a new fourfold TTB superstructure was found in small domains: Nb12W11O63 with an O/SM = 2.739 obviously accommodates a part of the sample’s metal excess compared to the stable phase Nb8W9O47.

Keywords

niobium tungsten oxide; pentagonal tunnels; tetragonal tungsten bronze; high-angle annular dark field detector; scanning transmission electron microscopy; HAADF-STEM; twinning; superstructure, battery material.

Subject

MATERIALS SCIENCE, General Materials Science

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