Sodium beta-alumina （SBA） is deposited on A1GaN/GaN by using a co-deposition process with sodium and Al2O3 as the precursors. The X-ray diffraction （XRD） spectrum reveals that the deposited thin film is amorphous....Sodium beta-alumina （SBA） is deposited on A1GaN/GaN by using a co-deposition process with sodium and Al2O3 as the precursors. The X-ray diffraction （XRD） spectrum reveals that the deposited thin film is amorphous. The binding energy and composition of the deposited thin film, obtained from the X-ray photoelectron spectroscopy （XPS） measurement, are consistent with those of SBA. The dielectric constant of the SBA thin film is about 50. Each of the capacitance voltage characteristics obtained at five different frequencies shows a high-quality interface between SBA and A1GaN. The interface trap density of metal-insulator-semiconductor high-electron-mobility transistor （MISHEMT） is measured to be （3.5-9.5）× 10^10 cm-2.eV-1 by the conductance method. The fixed charge density of SBA dielectric is on the order of 2.7× 1012 cm-2. Compared with the A1GaN/GaN metal-semiconductor heterostructure high-electron- mobility transistor （MESHEMT）, the A1GaN/GaN MISHEMT usually has a threshold voltage that shifts negatively. However, the threshold voltage of the A1GaN/GaN MISHEMT using SBA as the gate dielectric shifts positively from -5.5 V to -3.5 V. From XPS results, the surface valence-band maximum （VBM-EF） of A1GaN is found to decrease from 2.56 eV to 2.25 eV after the SBA thin film deposition. The possible reasons why the threshold voltage of A1GaN/GaN MISHEMT with the SBA gate dielectric shifts positively are the influence of SBA on surface valence-band maximum （VBM-EF）, the reduction of interface traps and the effects of sodium ions, and/or the fixed charges in SBA on the two-dimensional electron gas （2DEG）.展开更多
Upon heating, Mn atoms implanted into Na - beta- alumina diffuse inwards andoutwards with an activation energy of 0.96 eV, and substitute for Al3+ in the spinel layers of the crystal. For specimens annealed at 900 C, ...Upon heating, Mn atoms implanted into Na - beta- alumina diffuse inwards andoutwards with an activation energy of 0.96 eV, and substitute for Al3+ in the spinel layers of the crystal. For specimens annealed at 900 C, the optical absorption shows remarkable change in 190nm-400nm wavelength region. They fluoresce brightly green and a well- defined peak (at 525 nm) has been found in the radiative spectra.展开更多
Na-beta alumina batteries are one of the most promising technologies for renewable energy storage and grid applications. Na-beta alumina batteries can be constructed in either tubular or planar designs, depending on t...Na-beta alumina batteries are one of the most promising technologies for renewable energy storage and grid applications. Na-beta alumina batteries can be constructed in either tubular or planar designs, depending on the shape of the beta-alumina solid electrolyte. The tubular designs have been widely studied and developed since the 1960 s primarily because of their ease of sealing. However, planar designs are considered superior to tubular designs in terms of power output, cell packing, ease of assembly, thermal management, and other characteristics. Recently, Pacific Northwest National Laboratory has begun to develop high-performance planar Na-beta alumina batteries. In this paper, we provide an overview on the basic battery electrochemistry, solid electrolyte synthesis and fabrication, and our recent progress in developing planar batteries. Future trends for further technology improvement will also be presented.展开更多
Sodium beta alumina（Na-β-alumina） films were synthesized by heat treatment of NaAl6O（9.5）and γ-NaA1O2 films at temperatures of 1 373-1 573 K.Single-phase γ-NaA1O2 and NaAl6O（9.5） films were prepared by laser ...Sodium beta alumina（Na-β-alumina） films were synthesized by heat treatment of NaAl6O（9.5）and γ-NaA1O2 films at temperatures of 1 373-1 573 K.Single-phase γ-NaA1O2 and NaAl6O（9.5） films were prepared by laser chemical vapor deposition at the deposition temperatures of 976 and 1 100 K,respectively.Subsequent heat treatment of the films resulted in the formation of Na-β-alumina with α-Al2O3 at temperatures above 1 373 K for NaAl6O（9.5） and 1 473 K for γ-NaA1O2.On heat treatment at temperatures of 1 473-1 573 K,the faceted morphology with terraces of the as-deposited（110）-oriented γ-NaAlO2 films transformed to a porous morphology with platelet grains comprising Na-β-alumina and α-Al2O3.On heat treatment at temperatures of1 373-1 473 K,the pyramidal,faceted grains of as-deposited NaAl6O（9.5） films transformed to planer,shapeanisotropic morphology in the film of mixed Na-β-alumina and α-Al2O3.A dense morphology was observed in both the as-deposited and heat-treated NaAl6O（9.5） films.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.50932002)
文摘Sodium beta-alumina （SBA） is deposited on A1GaN/GaN by using a co-deposition process with sodium and Al2O3 as the precursors. The X-ray diffraction （XRD） spectrum reveals that the deposited thin film is amorphous. The binding energy and composition of the deposited thin film, obtained from the X-ray photoelectron spectroscopy （XPS） measurement, are consistent with those of SBA. The dielectric constant of the SBA thin film is about 50. Each of the capacitance voltage characteristics obtained at five different frequencies shows a high-quality interface between SBA and A1GaN. The interface trap density of metal-insulator-semiconductor high-electron-mobility transistor （MISHEMT） is measured to be （3.5-9.5）× 10^10 cm-2.eV-1 by the conductance method. The fixed charge density of SBA dielectric is on the order of 2.7× 1012 cm-2. Compared with the A1GaN/GaN metal-semiconductor heterostructure high-electron- mobility transistor （MESHEMT）, the A1GaN/GaN MISHEMT usually has a threshold voltage that shifts negatively. However, the threshold voltage of the A1GaN/GaN MISHEMT using SBA as the gate dielectric shifts positively from -5.5 V to -3.5 V. From XPS results, the surface valence-band maximum （VBM-EF） of A1GaN is found to decrease from 2.56 eV to 2.25 eV after the SBA thin film deposition. The possible reasons why the threshold voltage of A1GaN/GaN MISHEMT with the SBA gate dielectric shifts positively are the influence of SBA on surface valence-band maximum （VBM-EF）, the reduction of interface traps and the effects of sodium ions, and/or the fixed charges in SBA on the two-dimensional electron gas （2DEG）.
文摘Upon heating, Mn atoms implanted into Na - beta- alumina diffuse inwards andoutwards with an activation energy of 0.96 eV, and substitute for Al3+ in the spinel layers of the crystal. For specimens annealed at 900 C, the optical absorption shows remarkable change in 190nm-400nm wavelength region. They fluoresce brightly green and a well- defined peak (at 525 nm) has been found in the radiative spectra.
基金supported by the US Department of Energy’s(DOE’s)Advanced Research Projects Agency-Energy(ARPA-E)Office of Electricity Delivery&Energy Reliability(OE)
文摘Na-beta alumina batteries are one of the most promising technologies for renewable energy storage and grid applications. Na-beta alumina batteries can be constructed in either tubular or planar designs, depending on the shape of the beta-alumina solid electrolyte. The tubular designs have been widely studied and developed since the 1960 s primarily because of their ease of sealing. However, planar designs are considered superior to tubular designs in terms of power output, cell packing, ease of assembly, thermal management, and other characteristics. Recently, Pacific Northwest National Laboratory has begun to develop high-performance planar Na-beta alumina batteries. In this paper, we provide an overview on the basic battery electrochemistry, solid electrolyte synthesis and fabrication, and our recent progress in developing planar batteries. Future trends for further technology improvement will also be presented.
基金Funded by the Ministry of Education,Culture,Sports,Science and Technology,a Grant-in-Aid for Challenging Exploratory Research(No.26560235)the ARCMG–IMR Cooperative Program(No.14G0402)of Tohoku Universitythe China Scholarship Council and the 111 Project(No.B13035)of China
文摘Sodium beta alumina（Na-β-alumina） films were synthesized by heat treatment of NaAl6O（9.5）and γ-NaA1O2 films at temperatures of 1 373-1 573 K.Single-phase γ-NaA1O2 and NaAl6O（9.5） films were prepared by laser chemical vapor deposition at the deposition temperatures of 976 and 1 100 K,respectively.Subsequent heat treatment of the films resulted in the formation of Na-β-alumina with α-Al2O3 at temperatures above 1 373 K for NaAl6O（9.5） and 1 473 K for γ-NaA1O2.On heat treatment at temperatures of 1 473-1 573 K,the faceted morphology with terraces of the as-deposited（110）-oriented γ-NaAlO2 films transformed to a porous morphology with platelet grains comprising Na-β-alumina and α-Al2O3.On heat treatment at temperatures of1 373-1 473 K,the pyramidal,faceted grains of as-deposited NaAl6O（9.5） films transformed to planer,shapeanisotropic morphology in the film of mixed Na-β-alumina and α-Al2O3.A dense morphology was observed in both the as-deposited and heat-treated NaAl6O（9.5） films.
