Reduction of the TiO2-x melting temperature induced by oxygen deficiency with implications on experimental data accuracy and structural transition processes

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2014-06, Vol.8 (6), p.549-553
• Main Authors: Knaup, J. M., Marx, J., Frauenheim, T.
• Format: Article
• Language: English
• Subjects: Ceramic sintering; ceramics; density-functional based tight binding; flash sintering; Magnéli phase; Melting; melting point; memristors; Metal oxides; molecular dynamics; Phase transitions; TiO2
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.201409042

Molecular dynamics simulations show a clear reduction of the melting temperature of rutile TiO2 induced by O deficiency. The observed effect is considerably stronger than reported in the experimental literature. This difference may be caused by a lack of knowledge of the O content at the melting point during experiments. In combination with temperature induced reduction, the melting temperature reduction poses questions about the process of Magnéli phase formation in TiO2 memristor devices. Using TiO2 as a model for transition metal oxide ceramics, we propose a mechanism for the flash sintering process. Time evolution of the Ti–Ti g (r) at 2500 K at 6.9% and 9,3% O deficiency during MD simulation at the 0 K volume. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) Part of Focus Issue on “Functional Oxides” (Eds.: T. Frauenheim, J. M. Knaup, P. Broqvist, S. Ramanathan) The melting of metal oxides has a crucial influence on ceramics production but may also be an important step in the phase transitions governing the function of memristors. Molecular dynamics simulation of rutile titanium dioxide shows a stronger reduction of the melting temperature induced by O deficiency than experimental data. The authors propose an explanation of this difference based on the well‐known thermal reduction effect.