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Botella, P., Enrichi, F., Vomiero, A., Muñoz-Santiuste, J. E., Garg, A. B., Arvind, A., . . . Errandonea, D. (2020). Investigation on the Luminescence Properties of InMO4 (M = V5+, Nb5+, Ta5+) Crystals Doped with Tb3+ or Yb3+ Rare Earth Ions. ACS omega, 5(5), 2148-2158
Open this publication in new window or tab >>Investigation on the Luminescence Properties of InMO(M = V5+, Nb5+, Ta5+) Crystals Doped with Tb3+ or Yb3+ Rare Earth Ions
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2020 (English)In: ACS omega, ISSN 2470-1343, Vol. 5, no 5, p. 2148-2158Article in journal (Refereed) Published
Abstract [en]

We explore the potential of Tb- and Yb-doped InVO4, InTaO4, and InNbO4 for applications as phosphors for light-emitting sources. Doping below 0.2% barely change the crystal structure and Raman spectrum but provide optical excitation and emission properties in the visible and near-infrared (NIR) spectral regions. From optical measurements, the energy of the first/second direct band gaps was determined to be 3.7/4.1 eV in InVO4, 4.7/5.3 in InNbO4, and 5.6/6.1 eV in InTaO4. In the last two cases, these band gaps are larger than the fundamental band gap (being indirect gap materials), while for InVO4, a direct band gap semiconductor, the fundamental band gap is at 3.7 eV. As a consequence, this material shows a strong self-activated photoluminescence centered at 2.2 eV. The other two materials have a weak self-activated signal at 2.2 and 2.9 eV. We provide an explanation for the origin of these signals taking into account the analysis of the polyhedral coordination around the pentavalent cations (V, Nb, and Ta). Finally, the characteristic green (5D4 → 7FJ) and NIR (2F5/2 → 2F7/2) emissions of Tb3+ and Yb3+ have been analyzed and explained.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-77773 (URN)10.1021/acsomega.9b02862 (DOI)32064375 (PubMedID)
Note

Validerad;2020;Nivå 2;2020-02-19 (johcin)

Available from: 2020-02-19 Created: 2020-02-19 Last updated: 2020-02-19Bibliographically approved
Santiago, A., Tranquilin, R., Botella, P., Manjón, F., Errandonea, D., Paskocimas, C., . . . Bomio, M. (2020). Spray pyrolysis synthesis and characterization of Mg1-xSrxMoO4 heterostructure with white light emission. Journal of Alloys and Compounds, 813, Article ID 152235.
Open this publication in new window or tab >>Spray pyrolysis synthesis and characterization of Mg1-xSrxMoO4 heterostructure with white light emission
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2020 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 813, article id 152235Article in journal (Refereed) Published
Abstract [en]

Molybdates are inorganic materials with great potential in white phosphors application, being an alternative to traditional lighting sources. In this study, we report the synthesis and characterization of Mg1-xSrxMoO4 (x = 0, 0.25, 0.50, 0.75, and 1) powders with white light-emitting properties. Using X-ray diffraction, the formation of the monoclinic β-MgMoO4 phase was observed for x = 0 and the formation of the tetragonal scheelite phase of SrMoO4 was observed for x = 1. The formation of a heterostructure composed of both phases was found for compositions with x = 0.25, 0.50 and 0.75. Scanning electron microscopy images showed that the Mg1-xSrxMoO4 particles exhibit a spherical morphology formed by several primary nanoparticles. Raman scattering spectroscopy enabled the accurate identification of the Raman modes for different compositions and their assignment to either the SrMoO4 or β-MgMoO4 modes. The bandgap energies were determined to fluctuate between 4.25 eV and 4.44 eV, being influenced by the degree of structural disorder. The photoluminescence emission spectra of the nanoparticles showed neutral- and cool-white emission with high-quality white light (CRI > 80%). The samples synthesized with x ≤ 0.50 are potential materials for the application in LED lamps (6500 K) and pure white-light sources (5500 K).

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Ultrasonic spray pyrolysis, Raman spectroscopy, Photoluminescence, Molybdate, White emission
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-75975 (URN)10.1016/j.jallcom.2019.152235 (DOI)000490133900059 ()2-s2.0-85072037267 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-09-20 (johcin)

Available from: 2019-09-12 Created: 2019-09-12 Last updated: 2019-11-06Bibliographically approved
Botella, P., Errandonea, D., Garg, A., Rodriguez-Hernandez, P., Muñoz, A., Achary, S. & Vomiero, A. (2019). High-pressure characterization of the optical and electronic properties of InVO4, InNbO4, and InTaO4. SN Applied Sciences, 1(5), Article ID 389.
Open this publication in new window or tab >>High-pressure characterization of the optical and electronic properties of InVO4, InNbO4, and InTaO4
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2019 (English)In: SN Applied Sciences, ISSN 2523-3963, Vol. 1, no 5, article id 389Article in journal (Refereed) Published
Abstract [en]

We have studied the electronic properties at ambient pressure and under high pressure of InVO4, InNbO4, and InTaO4 powders, three candidate materials for hydrogen production by means of photocatalytic water splitting using solar energy. A combination of optical absorption and resistivity measurements and band structure calculations have allowed us to determine that these materials are wide band-gap semiconductors with a band-gap energy of 3.62(5), 3.63(5), and 3.79(5) eV for InVO4, InNbO4, and InTaO4, respectively. The last two compounds are indirect band-gap materials, and InVO4 is a direct band-gap material. The pressure dependence of the band-gap energy and the electrical resistivity have been determined too. In the three compounds, the band gap opens under compression until reaching a critical pressure, where a phase transition occurs. The structural transition triggers a band-gap collapse larger than 1.2 eV in the three materials, being the abrupt decrease in the band-gap energy related to an increase in the pentavalent cation coordination number. The phase transitions also cause changes in the electrical resistivity, which can be correlated with changes induced by pressure in the band structure. An explanation to the reported results is provided based upon ab initio calculations. The conclusions attained are of significance for technological applications of the studied oxides.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Wolframite, Band gap, optical properties, High pressure, Phase transition, Electronic properties
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-73617 (URN)10.1007/s42452-019-0406-7 (DOI)000473581300007 ()
Note

Validerad;2019;Nivå 2;2019-08-16 (johcin)

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-08-16Bibliographically approved
Anzellini, S., Errandonea, D., MacLeod, S. G., Botella, P., Daisenberger, D., De’Ath, M., . . . Wilson, C. W. (2018). Phase diagram of calcium at high pressure and high temperature. Physical review materials, 2(8), Article ID 083608.
Open this publication in new window or tab >>Phase diagram of calcium at high pressure and high temperature
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2018 (English)In: Physical review materials, ISSN 2475-9953, Vol. 2, no 8, article id 083608Article in journal (Refereed) Published
Abstract [en]

Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murnaghan equation of state with a Berman-type thermal expansion model.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-70985 (URN)10.1103/PhysRevMaterials.2.083608 (DOI)000443148600002 ()2-s2.0-85059624404 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-09-25 (svasva)

Available from: 2018-09-25 Created: 2018-09-25 Last updated: 2019-03-27Bibliographically approved
Botella, P., Devaux, X., Dossot, M., Garashchenko, V., Beltzung, J. C., Soldatov, A. & Ananev, S. (2017). Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar. Physica status solidi. B, Basic research, 254(11), Article ID 1700315.
Open this publication in new window or tab >>Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar
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2017 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 11, article id 1700315Article in journal (Refereed) Published
Abstract [en]

Single-walled carbon nanotubes (SWCNTs) have been dynamically (shock) compressed to 0.5 Mbar, above the limit of their structural integrity. Two distinct types of material are identified by high-resolution transmission electron microscopy (HRTEM) and multi-wavelength Raman spectroscopy in the sample recovered after shock: multi-layer graphene (MLG) and a two-phase material composed of nano-clustered graphene and amorphous carbon whereas no diamond-like carbon or carbon nano-onions are found. Peak decomposition of the Raman spectra was used to estimate the coherent scatterers (clusters) size in MLG at 36 nm from the D- to G-band intensity ratio dependence on the photon excitation energy. Botella et al. (article no. 1700315) propose the peak fitting model for decomposition of the Raman spectra of highly disordered carbon material containing graphene nano-clusters and stress the importance of accounting for heptagonal- and pentagonal-ring defects in graphene layers for the analysis of such spectra. The cover image shows HRTEM images and the correspondent Raman spectra of the two types of material along with peak decomposition of the two-phase material with the peaks assigned to heptagons (a) and pentagons (b). Particulars of the SWCNTs transformation to other structural forms of carbon at high pressure/temperature are discussed

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-68344 (URN)10.1002/pssb.201700315 (DOI)
Note

Validerad;2017;Nivå 2;2017-11-21 (andbra)

Available from: 2018-04-13 Created: 2018-04-13 Last updated: 2018-05-04Bibliographically approved
Botella, P., Devaux, X., Dossot, M., Garashchenko, V., Beltzung, J. C., Soldatov, A. & Ananev, S. (2017). Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar. Physica status solidi. B, Basic research, 254(11), Article ID 1770259.
Open this publication in new window or tab >>Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar
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2017 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 11, article id 1770259Article in journal (Refereed) Published
Abstract [en]

Single-walled carbon nanotubes (SWCNTs) have been dynamically (shock) compressed to 0.5 Mbar, above the limit of their structural integrity. Two distinct types of material are identified by high-resolution transmission electron microscopy (HRTEM) and multi-wavelength Raman spectroscopy in the sample recovered after shock: multi-layer graphene (MLG) and a two-phase material composed of nano-clustered graphene and amorphous carbon whereas no diamond-like carbon or carbon nano-onions are found. Peak decomposition of the Raman spectra was used to estimate the coherent scatterers (clusters) size in MLG at 36 nm from the D- to G-band intensity ratio dependence on the photon excitation energy. Botella et al. (article no. 1700315) propose the peak fitting model for decomposition of the Raman spectra of highly disordered carbon material containing graphene nano-clusters and stress the importance of accounting for heptagonal- and pentagonal-ring defects in graphene layers for the analysis of such spectra. The cover image shows HRTEM images and the correspondent Raman spectra of the two types of material along with peak decomposition of the two-phase material with the peaks assigned to heptagons (a) and pentagons (b). Particulars of the SWCNTs transformation to other structural forms of carbon at high pressure/temperature are discussed

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-66624 (URN)10.1002/pssb.201770259 (DOI)000417609800010 ()
Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2019-04-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6930-8415

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