Influence of the Anatase and Rutile phases on the luminescent properties of rare-earth-doped TiO2 films

Zanatta, A. R.; Scoca, D.; Alvarez, F.

doi:10.1016/j.jallcom.2018.11.401

Cited by 15 publications

(4 citation statements)

References 38 publications

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“…The chemical composition of the as-deposited TiO 2 thin films and after the thermal annealing at ∼1000 °C ( ex situ ) was obtained from the XPS spectra. These analyses considered the Ti 2p doublets (2p 3/2 and 2p 1/2 orbitals) located at ∼459 and ∼464 eV, respectively, along with the following core levels: O 1s at ∼531 eV, Sm 4d at ∼132 eV, and Tb 4d at ∼150 eV. , According to the XPS analysis, all TiO 2 films were almost stoichiometric ([Ti] ∼30 ± 3 at. % and [O] ∼70 ± 7 at.…”

Section: Resultsmentioning

confidence: 99%

“…Likewise, the photoluminescence of the films was investigated, and the main results can be found elsewhere. 26,36 ■ ASSOCIATED CONTENT * sı Supporting Information…”

Section: ■ Summary and Conclusionmentioning

confidence: 99%

“…All films, as-deposited and after each thermal annealing step, were further investigated by Raman scattering (488.0 nm photon excitation) and UV–vis (∼300–700 nm wavelength range) optical transmission measurements. Likewise, the photoluminescence of the films was investigated, and the main results can be found elsewhere. , …”

Section: Experimental Detailsmentioning

confidence: 99%

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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

et al. 2020

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The role played by oxygen vacancies and rare earth (RE) elements in the anatase-to-rutile (A–R) phase transformation of titanium dioxide (TiO2) is still a matter of controversy. Here, we report the A–R transformation of TiO2 thin solid films as obtained by ion beam sputtering a RE-decorated titanium target in an oxygen-rich atmosphere. The samples correspond to undoped, single-doped (Sm, Tm, and Tb), and codoped (Sm:Tb, Sm:Tm, and Sm:Tb:Tm) TiO2 films. In the as-prepared form, the films are amorphous and contain ∼0.5 at. % of each RE. The structural modifications of the TiO2 films due to the RE elements and the annealing treatments in an oxygen atmosphere are described according to the experimental results provided by Raman scattering, X-ray photoelectron spectroscopy, and optical measurements. The A–R transformation depends on both the annealing temperature and the characteristics of the undoped, single-doped, and codoped TiO2 films. As reported in the literature, the A–R transformation can be inhibited or enhanced by the presence of impurities and is mostly related to energetic contributions. The experimental results were analyzed, considering the essential and stabilizing role of the entropy of mixing in the A–R transformation due to the introduction of more and multiple quantum states originated in vacancies and impurities in the anatase phase.

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Section: Resultsmentioning

confidence: 99%

“…Likewise, the photoluminescence of the films was investigated, and the main results can be found elsewhere. 26,36 ■ ASSOCIATED CONTENT * sı Supporting Information…”

Section: ■ Summary and Conclusionmentioning

confidence: 99%

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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

et al. 2020

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“…ART of TiO 2 at high temperature could be controlled by the addition of metal ions, suitable chemical modifiers and an appropriate synthesis method [13]. Doping with metal ions is a one of the profitable ways to retard the ART [14,21,[23][24][25][26][27][28][29][30][31]. Metal ions could improve the thermal stability of TiO 2 through the reduction in contact points, and nucleation sites [32].Generally, doping of an element with higher oxidation state compared to Ti 4+ would improve charge carrier separation on the photocatalyst surface [33].…”

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Mo doped TiO₂: impact on oxygen vacancies, anatase phase stability and photocatalytic activity

et al. 2020

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This work outlines an experimental and theoretical investigation of the effect of molybdenum (Mo) doping on the oxygen vacancy formation and photocatalytic activity of TiO 2 . Analytical techniques such as x-ray diffraction (XRD), Raman, x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to probe the anatase to rutile transition (ART), surface features and optical characteristics of Mo doped TiO 2 (Mo-TiO 2 ). XRD results showed that the ART was effectively impeded by 2 mol% Mo doping up to 750°C, producing 67% anatase and 33% rutile. Moreover, the crystal growth of TiO 2 was affected by Mo doping via its interaction with oxygen vacancies and the Ti-O bond. The formation of Ti-O-Mo and Mo-Ti-O bonds were confirmed by XPS results. Phonon confinement, lattice strain and non-stoichiometric defects were validated through the Raman analysis. DFT results showed that, after substitutional doping of Mo at a Ti site in anatase, the Mo oxidation state is Mo 6+ and empty Mo-s states emerge at the titania conduction band minimum. The empty Mo-d states overlap the anatase conduction band in the DOS plot. A large energy cost, comparable to that computed for pristine anatase, is required to reduce Mo-TiO 2 through oxygen vacancy formation. Mo 5+ and Ti 3+ are present after the oxygen vacancy formation and occupied states due to these reduced cations emerge in the energy gap of the titania host. PL studies revealed that the electron-hole recombination process in Mo-TiO 2 was exceptionally lower than that of TiO 2 anatase and rutile. This was ascribed to introduction of 5s gap states below the CB of TiO 2 by the Mo dopant. Moreover, the photo-generated charge carriers could easily be trapped and localised on the TiO 2 surface by Mo 6+ and Mo 5+ ions to improve the photocatalytic activity. coatings [8,9]. The most commonly existing crystalline polymorphs of TiO 2 are anatase, rutile and brookite [10][11][12]. Anatase is accepted to be the more active phase of TiO 2 and is preferred by the ceramic industries to fabricate light active antimicrobial indoor building materials such as ceramics, glass, tiles and sanitary surfaces [13,14]. This requires thermal stability of the anatase phase under typical ceramic processing conditions. TiO 2 anatase is mainly fabricated at low calcination temperatures (∼500°C) to prevent the anatase to rutile phase transition (ART) [15][16][17], which produces the less photo-active rutile phase. The photo-activity of anatase arises from its appropriate band edge positions, electron affinity, ionisation potential, and the long lifetime of charge carriers [10,12,18]. Moreover, transient photo-conductance analysis has revealed that the electron-hole recombination phenomena in anatase (101) phase is much slower compared to rutile (110), which is credited in part to the indirect band gap of anatase [11,19].The unit cells of anatase and rutile phases are composed of TiO 6 octahedra with titanium atoms at the centre and oxygen atoms at the vertices [20]. Both anatase and rutile have a t...

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Role of Eu and Fe in TiO2 for magneto-opto-electronic applications

Rehani

Saxena²,

Balal

et al. 2022

Appl. Phys. A

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Influence of the Anatase and Rutile phases on the luminescent properties of rare-earth-doped TiO2 films

Cited by 15 publications

References 38 publications

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

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

Mo doped TiO₂: impact on oxygen vacancies, anatase phase stability and photocatalytic activity

Role of Eu and Fe in TiO2 for magneto-opto-electronic applications

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Influence of the Anatase and Rutile phases on the luminescent properties of rare-earth-doped TiO2 films

Cited by 15 publications

References 38 publications

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

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

Mo doped TiO2: impact on oxygen vacancies, anatase phase stability and photocatalytic activity

Role of Eu and Fe in TiO2 for magneto-opto-electronic applications

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

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

Mo doped TiO₂: impact on oxygen vacancies, anatase phase stability and photocatalytic activity