Spectroscopic characterization of a multiband complex oxide: Insulating and conducting cement 12CaO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>·</mml:mo></mml:math>7Al<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>

McLeod, John A.; Buling, Anna; Kurmaev, E.Z.; Sushko, Peter V.; Neumann, M.; Finkelstein, L. D.; Kim, Sung Wng; Hosono, Hideo; Moewes, A.

doi:10.1103/physrevb.85.045204

Cited by 19 publications

(13 citation statements)

References 43 publications

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“…The X-ray photoelectron spectra of the dried gel and the crystallized film are shown in 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 7 concentration of these species being too small compared to the ones of the framework oxygen ions [19].…”

Section: Resultsmentioning

confidence: 99%

“…The X-ray photoelectron spectra of the dried gel and the crystallized film are shown in No separate peak was observed for the extra-framework oxygen site probably due to the binding energies of the O 2-1s level being too close to that of the lattice and/or the 7 concentration of these species being too small compared to the ones of the framework oxygen ions [19].…”

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confidence: 99%

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Vibrational spectroscopic studies on crystallisation of sol–gel derived thin films of calcia–alumina binary compound

Feizi

Ojeda

Ray

2014

J Mater Sci: Mater Electron

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Abstract:An optimized sol-gel process has now been developed to produce homogeneous thin films of calcium aluminate binary 12CaO.7Al2O3 compound, 12CaO.7Al2O3, on magnesium oxide substrates via spin coating. Fourier transform infrared (FTIR) and Raman spectroscopies have been employed to investigate the effect of annealing temperature and duration on the phase transformations in the films. Heat treatment at 13000C under air atmosphere for 2 hours produced single-phase 12CaO.7Al2O3 films. However, annealing at a lower temperature of 11000C in air for a period of 4 hours in total resulted in the crystallization of 5CaO.3Al2O3 rather than 12CaO.7Al2O3. The Xray photoelectron spectrum of the thin film annealed at 13000C corresponds to the binding energies of C12A7 compound. The annealing temperature of 13000C for 2 hours is found to be sufficient for formulating single phase calcia-alumina binary films in correct stoichiometric ratio of 12:7. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 While the fabrication of C12A7 single crystal and polycrystalline bulk has been studied extensively during the last few years, studies on the fabrication of C12A7 thin films are rather limited. The thin film fabrication techniques include pulsed laser deposition and sol-gel method, and magnesium oxide (MgO) single crystal is used as the substrate. A heat treatment temperature of 1100 o C in air atmosphere has been suggested for the crystallization of amorphous thin films prepared via pulsed laser deposition [7,8], while this temperature is mentioned to be too low for the crystallization of the sol-gel derived films [9]. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems CorporationThe fabrication of C12A7 thin films via sol-gel technique has been previously reported employing ethyl acetoacetate (EAA) and aluminium sec-butoxide (ASB) as a chelating agent and the main precursor of aluminium oxide, respectively in the molar ratio of 1:1 in an ethanol solvent.Hydrochloric acid (HCl) was used as the pH regulator [10,11]. However, our initial attempt in the deposition of C12A7 thin films on the MgO substrates using this recipe resulted in the formation of discontinuous films with dendritic growth behaviour. Therefore, the solution recipe was modified in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 order to increase the homogeneity and continuity of the films. Highly stable spreading solutions for spin coating were obtained using the modified recipe without the need for the addition of acid. This article presents the Fourier transform infrared (FTIR) and Raman spectroscopy investigations into the effect of heat treatm...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Vibrational spectroscopic studies on crystallisation of sol–gel derived thin films of calcia–alumina binary compound

Feizi

Ojeda

Ray

2014

J Mater Sci: Mater Electron

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“…2 out of 12 cages are randomly occupied with 2 extra framework O 2-ions in the stoichiometric composition in order to neutralise the positive charge of the framework. The non-stoichiometric composition can contain OH -ions in addition to O 2-ions [3]. Various techniques have been successfully developed to introduce anions/electrons as a substitute for O 2-ions without altering the structure of the framework [4,5].…”

Section: Introductionmentioning

confidence: 99%

Extraction of the optical parameters of sol–gel processed 12CaO·7Al2O3 thin film for optoelectronic applications

Feizi

Ray

2015

J Mater Sci: Mater Electron

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Optical constants refractive index and extinction coefficient of sol-gel processed polycrystalline 12CaOÁ7Al 2 O 3 (C12A7) thin films with crystallite grain of 57 nm in size have been determined from optical transmittance and reflectance spectra experimentally obtained at normal incidence and the averaged value of refractive index below the band edge was found to be *2.15. The dispersion relation between refractive index and incident wavelength was examined in terms of both Cauchy-Sellmeier and single-effective oscillator models. The relation between refractive index and band gap energy at different temperatures in the range of 25-300°C was studied. The refractive index showed a positive temperature dependency in the studied temperature range.

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“…The chemical formula of a unit cell for mayenite in a fully oxidized state is represented by a positively charged lattice framework and two endohedral oxygen ions, [Ca 24 Al 28 O 64 ] 4+ [ 10 2O…”

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confidence: 99%

“…The polaron uses hopping motion to reach the neighboring cage by quantum tunneling, contributing to the conductivity. As electron doping proceeds as described by the formula [Ca 24 Al 28 O 64 ] 4+ [2(1 − x)O 2− + 4x(e − )], it exhibits insulator-to-metal transition [8], eventually exhibiting superconductivity with a transition temperature of ∼0.4 K in the compound with maximum doping (x ≃ 1, corresponding to an electron concentration of ∼2×10 21 cm −3 ) [11].…”

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confidence: 99%

Cage electron-hydroxyl complex state as electron donor in mayenite

et al. 2016

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It is inferred from the chemical shift of muon spin rotation (µSR) spectra that muons implanted in pristine (fully oxidized) mayenite, [Ca 12 Al 14 O 32 ] 2+ [ 5 O 2− ] (C12A7, with referring to the vacant cage), are bound to O 2− at the cage center to form OMu − (where Mu represents muonium, a muonic analog of the H atom). However, an isolated negatively charged state (Mu − , an analog of H − ) becomes dominant when the compound approaches the state of electride [Ca 12 Al 14 O 32 ] 2+ [ 4 2e − ] as a result of the reduction process. Moreover, the OMu − state in the pristine specimen exhibits depolarization of paramagnetic origin at low temperatures (below ∼30 K), indicating that OMu − accompanies a loosely bound electron in the cage that can be thermally activated. This suggests that interstitial muons (and hence H) forming a "cage electron-hydroxyl" complex can serve as electron donors in C12A7.

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Spectroscopic characterization of a multiband complex oxide: Insulating and conducting cement 12CaO·7Al2O3

Cited by 19 publications

References 43 publications

Vibrational spectroscopic studies on crystallisation of sol–gel derived thin films of calcia–alumina binary compound

Vibrational spectroscopic studies on crystallisation of sol–gel derived thin films of calcia–alumina binary compound

Extraction of the optical parameters of sol–gel processed 12CaO·7Al2O3 thin film for optoelectronic applications

Cage electron-hydroxyl complex state as electron donor in mayenite

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