Role of Rare Earth Elements and Entropy on the Anatase-To-Rutile Phase Transformation of TiO<sub>2</sub> Thin Films Deposited by Ion Beam Sputtering

Scoca, D.; Cemin, Felipe; Bilmes, Sara A.; Figueroa, Carlos A.; Zanatta, A. R.; Alvarez, F.

doi:10.1021/acsomega.0c03431

Cited by 13 publications

(18 citation statements)

References 72 publications

(146 reference statements)

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“…Anatase formation mainly relies on the distorted and strained anatase-like structures in the amorphous samples. The mechanism of ART mainly relies on the topological arguments called edge-to-vertex r-ratio linking the TiO 6 octahedral units . The anatase and rutile crystalline polymorphs share four and two edges, respectively.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The anatase and rutile crystalline polymorphs share four and two edges, respectively. The rutile phase would emerge as the edge-to-vertex linked percentage is relatively smaller in the amorphous precursor during calcination . Conversely, the anatase phase would emerge, as the edge-to-vertex linked percentage is higher.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The internal energy (Δ U ) would be higher with respect to the increase in temperature, and therefore, Δ S mix should be higher to inhibit the ART. Scoca et al suggested that Δ S mix was not sufficient to compensate the increase in Δ U at high calcination temperatures, endorsing the ART of rare-earth-metal-doped TiO 2 …”

Section: Results and Discussionmentioning

confidence: 99%

“…The mechanism of ART mainly relies on the topological arguments called edge-tovertex r-ratio linking the TiO 6 octahedral units. 52 The anatase and rutile crystalline polymorphs share four and two edges, respectively. The rutile phase would emerge as the edge-tovertex linked percentage is relatively smaller in the amorphous precursor during calcination.…”

Section: Resultsmentioning

confidence: 99%

“…The rutile phase would emerge as the edge-tovertex linked percentage is relatively smaller in the amorphous precursor during calcination. 52 Conversely, the anatase phase would emerge, as the edge-to-vertex linked percentage is higher. ART of TiO 2 is commonly prevented at adiabatic temperatures (low calcination temperatures) by reaching a metastable thermodynamic equilibrium between the defects and oxygen atoms.…”

Section: Resultsmentioning

confidence: 99%

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New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO₂

et al. 2021

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The impact of iridium (Ir) doping on the oxygen vacancies, relative stability, crystallite size, surface area, and anatase-to-rutile transition of TiO 2 was comprehensively investigated in this study. Ir-doped TiO 2 (Ir-TiO 2 ) was synthesized through a sol−gel technique, and the samples were annealed in the temperature range of 400−700 °C. Density functional theory calculations showed that the energy cost of an oxygen vacancy formation for Ir-TiO 2 was lower, as compared to that of the pristine TiO 2 , with the formation of Ir 3+ states in the band gap. Ir could provide more rutile nucleation sites and accelerate the rutile formation through the crystal strain relaxation. The entropy of mixing was reduced by the incorporation of Ir, which could induce the rutile formation with an increase in Gibbs free energy at temperatures below the normal phase transition temperature for pure TiO 2 . The rutile formation of Ir-TiO 2 could take place at a low annealing temperature (400 °C) compared to pristine TiO 2 (600 °C), indicating that the activation energy for phase transition could be decreased by incorporating Ir. XPS revealed the spin−orbit coupling of Ir 4f peaks, Ir 4f 7/2 (61.96 eV) and Ir 4f 5/2 (64.77 eV), due to the presence of Ir 3+ . Raman studies indicated the formation of charge-compensating oxygen vacancies and the presence of d states by Ir doping. It is concluded that the defects originated because the incorporation of Ir could facilitate rutile nucleation sites and thereby accelerate the phase transition through strain relaxation.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO₂

et al. 2021

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Heterophase Interface and Surface Functionalization of TiO_x/TiSi_x Metastable Nanofilms

Echeverrigaray

Figueroa

Zanatta

et al. 2022

Adv Materials Inter

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In this paper, topographically asymmetric TiOx/TiSix metastable ultrathin (nano)films on SiO2/Si(100) are produced by controlling interface reactions through ion beam synthesis. The film growth process involves a dual ion beam system, combining Ar+ sputtering a Ti target and in situ postirradiation (Ar+ + H2+ ion etching) at normal incidence to modify the surface morphology. The film's production and characterization are challenging due to the formation of a complex mixed interface+layers (heterophases) containing nanocrystalline and amorphous compounds of Ti and Si. The results for different ion etching times (0–600 s) are systematically presented and analyzed. With the experimental+theoretical information, it is possible to deduce that the heterophase interface is originated by oxide intermixing in combination with the formation of titanium silicides taking place at the early stages of growth. The reactivity of oxygen and hydrogen species is the dominating factor influencing the metastable film growth mediated by solid‐state phase reactions. Given its crucial role at the (Ti/Si):O interface, the chemical route and control of intrinsic defects (non‐stoichiometry) are defined by domain ordering mechanisms followed by surface restructuring. In view of their main characteristics, taken altogether, the current functional metastable films represent a promising alternative for high‐performance photonic and optoelectronic applications.

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Illuminating Pathways to Dynamic Nanotribology: Light‐Mediated Active Control of Interfacial Friction with Nanosuspensions

Leidens,

Michels,

Machado

et al. 2024

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Active control of nanotribological properties is a challenge. Materials responsive to external stimuli may catalyze this paradigm shift. Recently, the nanofriction of a thin film is modulated by light, ushering in phototribology. This frontier is expanded here, by investigating photoactive nanoparticles in lubricants to confer similar functionality to passive surfaces. Quartz‐crystal microbalance (QCM) is employed to assess the phototribological behavior of aqueous suspensions of titanium dioxide nanoparticles. A comparison of dark and illuminated conditions provides the first demonstration of tuning the interfacial friction in solid‐nanosuspension interfaces by light. Cyclic tests reveal reversible transitions between higher (dark) and lower friction (illuminated) regimes. These transitions are underpinned by transient states with surface charge variations, as confirmed by Zeta potential measurements. The accumulated surface charge increases repulsion within the system and favors sliding. Upon cessation of illumination, the system returns to its prior equilibrium state. These findings impact not only nanotribology but nanofluidics and nanorheology. Furthermore, the results underscore the need to consider light‐induced effects in other scenarios, including the calculation of activity coefficients of photoactive suspensions. This multifaceted study introduces a new dimension to in operando frictional tuning, beckoning a myriad of applications and fundamental insights at the nanoscale.

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Role of Rare Earth Elements and Entropy on the Anatase-To-Rutile Phase Transformation of TiO₂ Thin Films Deposited by Ion Beam Sputtering

Cited by 13 publications

References 72 publications

New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO₂

New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO₂

Heterophase Interface and Surface Functionalization of TiO_x/TiSi_x Metastable Nanofilms

Illuminating Pathways to Dynamic Nanotribology: Light‐Mediated Active Control of Interfacial Friction with Nanosuspensions

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Role of Rare Earth Elements and Entropy on the Anatase-To-Rutile Phase Transformation of TiO2 Thin Films Deposited by Ion Beam Sputtering

Cited by 13 publications

References 72 publications

New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO2

New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO2

Heterophase Interface and Surface Functionalization of TiOx/TiSix Metastable Nanofilms

Illuminating Pathways to Dynamic Nanotribology: Light‐Mediated Active Control of Interfacial Friction with Nanosuspensions

Contact Info

Product

Resources

About

Role of Rare Earth Elements and Entropy on the Anatase-To-Rutile Phase Transformation of TiO₂ Thin Films Deposited by Ion Beam Sputtering

New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO₂

New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO₂

Heterophase Interface and Surface Functionalization of TiO_x/TiSi_x Metastable Nanofilms