Discovery of a ternary pseudobrookite phase in the earth-abundant Ti–Zn–O system. Issue 4 (21st December 2015)

• Record Type: Journal Article
• Authors: Perry, Nicola H.; Stevanovic, Vladan; Lim, Linda Y.; Mason, Thomas O.
• Is Part Of: Dalton transactions. Volume 45:Issue 4(2016)
• Page Start: 1572
• Page End: 1581
• Publication Date: 2015-12-21
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt04145g
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : We apply a combined theoretical and experimental approach to the search for "missing", stable materials within the ternary Zn–Ti–O chemical system, leading to the discovery of a new pseudobrookite phase, Zn x Ti3− x o5− δ . Abstract : We combine theory with experiment in searching for "missing", stable materials within the Zn–Ti–O chemical system, leading to the discovery of a new pseudobrookite phase, Zn x Ti3− x O5− δ . This ternary system was chosen for (1) technological relevance, (2) earth abundance, and (3) the fact that many compounds in this system are predicted from enthalpies of formation to be borderline stable, suggesting an important role of entropic contributions in their stabilization and making this chemical system a perfect test bed for exploring the limits of theoretical predictions. The initial set of exploratory experimental syntheses, via sintering in evacuated ampoules and quenching, resulted in a single phase Zn x Ti3− x O5− δ composition with x ≈ 0.6 and an almost stoichiometric oxygen content, as evaluated by X-ray fluorescence, energy dispersive spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The theoretically calculated lowest energy crystal structure for the closest stoichiometric ZnTi5 O10 composition matched that measured experimentally by synchrotron X-ray diffraction (allowing for differences attributable to cation disorder). The measured broad optical absorption, n-type electrical conductivity, and stability in acidic media are comparable to those of other ternary pseudobrookites and Ti–O Magnéli phases, suggesting comparable applicability as a robust electrode or catalyst support in electrochemical devices or water remediation. However, the new phase decomposes upon heating in air as it oxidizes. The success of the present approach to identify a "missing material" in an earth-abundant and applications-rich system suggests that future efforts to experimentally realize and theoretically confirm missing materials in this and similar systems are warranted, both scientifically and technologically.