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arXiv · 1908.10067

A combinatorial guide to phase formation and surface passivation of tungsten titanium oxide prepared by thermal oxidation

Sebastian Siol·Noémie Ott·Michael Stiefel·Max Döbeli·Patrik Schmutz·Lars P. H. Jeurgens·Claudia Cancellieri
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Abstract

TiO$_2$ and WO$_3$ are two of the most important earth-abundant electronic materials with applications in countless industries. Recently alloys of WO$_3$ and TiO$_2$ have been investigated leading to improvements of key performance indicators for a variety of applications ranging from photo-electrochemical water splitting to electrochromic smart windows. These positive reports and the complexity of the ternary W-Ti-O phase diagram motivate a comprehensive experimental screening of this phase space. Using combinatorial thermal oxidation of solid solution W$_{1-x}$Ti$_{x}$ precursors combined with bulk and surface analysis mapping we investigate the oxide phase formation and surface passivation of tungsten titanium oxide in the entire compositional range from pure WO$_3$ to TiO$_2$. The system shows a remarkable structural transition from monoclinic over cubic to tetragonal symmetry with increasing Ti concentration. In addition, a strong Ti surface enrichment is observed for precursor Ti-concentrations in excess of 55 at.%, resulting in the formation of a protective rutile-structured TiO$_2$ surface layer. Despite the structural transitions, the optical properties of the oxide alloys remain largely unaltered demonstrating an independent control of multiple functional properties in W$_{1-x}$Ti$_{x}$O$_{n}$. The results from this study provide valuable guidelines for future development of W$_{1-x}$Ti$_{x}$O$_{n}$ for electronic and energy applications, but also novel engineering approaches for surface functionalization and additive manufacturing of Ti-based alloys.

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Sebastian Siol, Noémie Ott, Michael Stiefel, Max Döbeli, Patrik Schmutz, Lars P. H. Jeurgens, Claudia Cancellieri. 2019-08-27. A combinatorial guide to phase formation and surface passivation of tungsten titanium oxide prepared by thermal oxidation. https://doi.org/10.1016/j.actamat.2019.12.026

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