Temperature dependence of the electronic structure of oxides: MgO, MgAl2O4and Al2O3

Bortz, Michael; French, Roger H.; Jones, David J.; Kasowski, R. V.; Ohuchi, F. S.

doi:10.1088/0031-8949/41/4/036

Cited by 141 publications

(62 citation statements)

References 15 publications

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“…Thibaudeau and Gervais [13] have performed ab initio calculations of infrared and Raman phonon modes in the normal cubic MgAl 2 O 4 spinel at the first Brillouin zone centre using density functional theory (DFT) with plane-wave basis and norm-conserving pseudopotentials. Bortz et al [14] have studied the room temperature optical reflectivity of MgO, MgAl 2 O 4 and α-Al 2 O 3 from 5 eV to 40 eV using a novel spectrophotometer with a laser plasma light source.…”

Section: Introductionmentioning

confidence: 99%

Structural, electronic and optical properties of spinel MgAl₂O₄ oxide

Hosseini

2008

Physica Status Solidi (b)

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The structure, band structure, total density of states, dielectric function, reflectivity, refractive index and loss function have been calculated for spinel MgAl2O4 oxide using density functional theory. The full‐potential linearized augmented plane wave method was used with the generalized gradient approximation. Calculations of the optical spectra have been performed for the energy range 0–40 eV. It is shown that the material is transparent at visible wavelengths and the dispersion curve of the refractive index is fairly flat in the long‐wavelength region and rises rapidly towards shorter wavelengths. The refractive index is 1.774 at 800 nm near the visible region. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Introductionmentioning

confidence: 99%

Structural, electronic and optical properties of spinel MgAl₂O₄ oxide

Hosseini

2008

Physica Status Solidi (b)

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“…The ICP elemental analysis data in Table 1 and FT-IR spectra in Figure 2 confirm To understand the shift of the CT band, it is necessary to consider the electronic structure of Sr 2 The calculated band structure and density of states (DOS) for the samples are shown in Figures 4 and 5, respectively. In Figure 4(a) and (b [24].…”

Section: Resultsmentioning

confidence: 97%

“…Despite the similar ionic radii of Zn 2+ (74 pm, coordination number (CN) = 4) and Mg 2+ (71 pm, CN = 4) and their identical valence state, the crystal and/or electronic structure of a material usually changes significantly when substitution occurs between Zn 2+ and Mg 2+ SiO 4 were both observed to be as low as 5 at.% [1]. MgAl 2 O 4 -ZnAl 2 O 4 is similar; the band gap of MgAl 2 O 4 is 7.8 eV [2] while that of ZnAl 2 O 4 is just 3.8-3.9 eV [3]. This implies that Zn 2+ plays a particular role in crystal and electronic structure changes in these systems.…”

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confidence: 99%

Investigation of the electronic structure and photoluminescence properties of Eu3+ in Sr2Mg1−x Zn x Si2O7 (0⩽ x ⩽ 1)

Zhang

Wang

2012

Chin. Sci. Bull.

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has been used as a structural probe because of its particularly sensitive emission [10][11][12]. In addition, the O 2 -Eu 3+ charge transfer (CT) transition involves both the luminescent center and host, so it can be used to probe the coupling between the luminescent center and host.In the present work, undoped and Eu 3+ -doped Sr 2 Mg 1x -Zn x Si 2 O 7 (0  x  1) samples were prepared. Inductively coupled plasma (ICP), Fourier transform infrared (FT-IR),

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“…Though a lot of work on the temperature dependence of the bandgap has been done in semiconductors, much less work has been done in insulators. One example is the work by Bortz et al, 25 which shows the bandgaps in MgO, MgAl 2 O 4 , and Al 2 O 3 decrease by ∼1 eV as the temperature is changed from 300 K to 1400 K, exhibiting roughly a linear dependence. Given that the color temperatures we report on suggest our samples obtain temperatures over 2000 K, we expect our band gaps could be decreasing by as much as a few eV.…”

Section: Discussionmentioning

confidence: 99%

Broadband, White Light Emission from Doped and Undoped Insulators

Tabanli

Cinkaya

Bílír

et al. 2017

ECS J. Solid State Sci. Technol.

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We present data on broadband, white light emission from insulating hosts under intense excitation in the near infrared in host materials that are undoped, partially-doped with rare earth ions, and that contain stoichiometric concentrations of rare earth ions. Much of the emission is found to have a blackbody-like structure in the visible and near infrared region. The origin of the emission as from a blackbody is also supported by the temporal characteristics of the emission in response to turning on and off the laser, and also by the dependence of the air pressure in the chamber. However, some of the data presented cannot be explained by blackbody emission alone, so other processes are proposed to explain the observed spectra. The role of the rare earth ion dopants in enhancing the broadband emission is also considered. Over the last several years, numerous works have reported a broadband, white-light emission from insulating powders under intense, near infrared (IR) excitation. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The materials investigated are usually nano-powders of insulators, such as yttrium oxide, yttrium silicate, Al 2 O 3 , GGG, and others, either pure or doped with rare earth ions (e.g. Er, Nd, Yb, Tm) or transition metal ions (e.g. Cr). Spectral and temporal characteristics of the broadband emission suggest that it is thermal in origin. One study on the origin of the emission, conducted by Debasu et al.,16 concluded that the emission is indeed blackbody emission, with temperatures in the range of ∼1200 K-1900 K. We have studied the white-light emission phenomenon in several host materials, both doped and undoped. In this work, we present results representative of this body of work, and we consider how these results fit into the blackbody model.For lighting applications, one of the main goals is the generation of high quality, white light with highest possible efficiency. Broadband white light based on blackbody-like emission can be of very high quality, but it is never efficient, especially compared to compact fluorescent or LED-based lighting. The white light we report on here is probably no different in that regard, and so it likely will be of little usefulness as a general lighting source. One difference between these emitters and tungsten-based blackbody sources is the means by which energy is delivered to the system; the energy source is a near infrared diode laser instead of electrical power converted to Joule heating, as in a tungsten lamp.Production of white light using near IR photons can occur in different ways. One method of recent interest is the upconversion process in rare earth doped systems that depend on energy transfer and/or excited state absorption to produce emission of high-energy photons. Usually, this occurs in systems co-doped with, for example, Yb, Er and Tm, 20,21 and the emission is exclusively from the f-f transitions of the dopant ions. The white light reported on here is generated in a fundamentally different way. The energy contained in the...

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Temperature dependence of the electronic structure of oxides: MgO, MgAl₂O₄and Al₂O₃

Cited by 141 publications

References 15 publications

Structural, electronic and optical properties of spinel MgAl₂O₄ oxide

Structural, electronic and optical properties of spinel MgAl₂O₄ oxide

Investigation of the electronic structure and photoluminescence properties of Eu3+ in Sr2Mg1−x Zn x Si2O7 (0⩽ x ⩽ 1)

Broadband, White Light Emission from Doped and Undoped Insulators

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Temperature dependence of the electronic structure of oxides: MgO, MgAl2O4and Al2O3

Cited by 141 publications

References 15 publications

Structural, electronic and optical properties of spinel MgAl2O4 oxide

Structural, electronic and optical properties of spinel MgAl2O4 oxide

Investigation of the electronic structure and photoluminescence properties of Eu3+ in Sr2Mg1−x Zn x Si2O7 (0⩽ x ⩽ 1)

Broadband, White Light Emission from Doped and Undoped Insulators

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Temperature dependence of the electronic structure of oxides: MgO, MgAl₂O₄and Al₂O₃

Structural, electronic and optical properties of spinel MgAl₂O₄ oxide

Structural, electronic and optical properties of spinel MgAl₂O₄ oxide