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| 3. |
- Bielecki, Johan, 1982, et al.
(author)
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Two-component heat diffusion observed in LaMnO3 and La0.7Ca0.3MnO3
- 2010
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In: Physical Review B Condensed Matter. - : Americal Physical Society. - 0163-1829 .- 1095-3795. ; 81:6, s. art. no. 064434-
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Journal article (other academic/artistic)abstract
- We investigate the low-temperature electron, lattice, and spin dynamics of LaMnO3 (LMO) and La0.7Ca0.3MnO3 (LCMO) by resonant pump-probe reflectance spectroscopy. Probing the high-spin d-d transition as a function of time delay and probe energy, we compare the responses of the Mott insulator and the double-exchange metal to the photoexcitation. Attempts have previously been made to describe the subpicosecond dynamics of colossal magnetoresistance manganites in terms of a phenomenological three-temperature model describing the energy transfer between the electron, lattice, and spin subsystems followed by a comparatively slow exponential decay back to the ground state. However, conflicting results have been reported. Here we first show clear evidence of an additional component in the long-term relaxation due to film-to-substrate heat diffusion and then develop a modified three-temperature model that gives a consistent account for this feature. We confirm our interpretation by using it to deduce the band gap in LMO. In addition, we also model the nonthermal subpicosecond dynamics, giving a full account of all observed transient features both in the insulating LMO and the metallic LCMO.
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| 4. |
- Carini, Giovanni, et al.
(author)
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Ultrasonic and hypersonic behaviours of borate glasses
- 2007
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In: Philosophical Magazine. - 1478-6435 .- 1478-6443. ; 87, s. 697-703
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Journal article (peer-reviewed)abstract
- Comparative measurements of Brillouin light scattering and ultrasound in (K2O)0.04(B2O3)0.96 and (Ag2O)0.14(B2O3)0.86 borate glasses as a function of temperature between 1.5 and 300 K reveal that distinct mechanisms regulate the temperature behaviours of the acoustic attenuation. In the MHz range the attenuation and the sound velocity are mainly governed by (i) quantum-mechanical tunnelling below 20 K, (ii) thermally activated relaxations between 20 and 200 K and (iii) vibrational inharmonicity at even higher temperatures. In the GHz range and in the temperature interval between 77 and 300 K, additional contributions besides the relaxation process must be taken into consideration to account for the hypersonic attenuation.
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- Gejke, Cecilia, 1973, et al.
(author)
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Lithium insertion in Sn-P and Sn-B-P oxide glasses
- 2000
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In: Lithium Batteries. Proceedings of the International Symposium (Electrochemical Society Proceedings). - 0161-6374. ; 99-25, s. 144-149.
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Conference paper (other academic/artistic)abstract
- The behaviour of electrodes based on Sn2P2O7 and Sn2BPO6 glasses during cycling were characterized with diffuse IR reflectance. By removing the electrodes from the half-cells at different stages of the electrochemical cycling it was possible to follow the development of the glass structures during lithium insertion and extraction. It was found that the local network structure around the phosphate groups in the glass experience structural changes by the lithium insertion. These changes are not fully recovered by lithium extraction during the first cycle and are likely related to the initial irreversible loss of capacitance of the electrodes.
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- Gejke, Cecilia, 1973, et al.
(author)
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Microscopic structure of tin-borate and tin-boratephosphate glasses
- 2003
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In: Journal of Power Sources. - 0378-7753. ; 119-121, s. 576-580.
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Journal article (peer-reviewed)abstract
- The structure of tin-borate and tin-borophosphate glasses has been examined with diffuse reflectance IR (DR-IR) and Raman spectroscopy. The basic network structure for these glasses is described as well as the positioning of tin in the network. Data suggests that the amount of phosphate present in the glass regulate the glass forming properties of tin. With borate as the dominating glass forming oxide, SnO acts like a glass former, but with increasing amount of phosphate SnO instead tends to behave as a network modifier.
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| 7. |
- Gejke, Cecilia, 1973, et al.
(author)
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Structural investigation of the Li+ ion insertion/extraction mechanism in Sn-based composite oxide glasses
- 2001
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In: Journal of Physics and Chemistry of Solids. - 0022-3697. ; 62, s. 1213-1218.
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Journal article (peer-reviewed)abstract
- The effect of lithium insertion for two Sn-based composite oxide glasses, Sn2BPO6 and Sn2P2O7, was examined during the first electrochemical discharge/charge cycle. Electrodes based on these glasses were analysed with micro-Raman spectroscopy at different steps during the cycle. In-situ X-ray diffraction has been used to confirm the amorphous state during the lithium insertion and extraction process. No alloy formation between Li and Sn could be discerned throughout the first cycle. It was found that when lithium enters the electrode, a reaction at the surface of the glass particles takes place resulting in Li3PO4, Li2O and SnO2 formation. The charge compensation mechanism is thought to be the reduction of Sn2+ to Sn. The formation of Li3PO4 is found to be irreversible and is as such partly responsible for the large observed capacity loss during the first cycle.
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| 8. |
- Gejke, Cecilia, 1973, et al.
(author)
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The effect of lithium insertion on the structure of tin oxide-based glasses
- 2001
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In: Journal of Power Sources. - 0378-7753. ; 97-98, s. 226-228.
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Journal article (peer-reviewed)abstract
- Two different SnO-based glasses, Sn2B3O6.5 and Sn2B2AlO6.5, have been examd. with FT-IR and Raman spectroscopy at different stages during the first electrochemical cycle. Some disruption of the connection between borate units in the network occurred during cycling. There was also an irreversible formation of Li3BO3 that can be related to the large capacity loss.
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| 10. |
- Karlsson, Maths, et al.
(author)
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Temperature-Dependent Infrared Spectroscopy of Proton-Conducting Hydrated Perovskite BaInxZr1-xO3-x/2 (x=0.10-0.75)
- 2010
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In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:13, s. 6177-6181
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Journal article (peer-reviewed)abstract
- We investigate the temperature dependence of the O-H stretch band in the infrared absorbance spectra of the proton-conducting hydrated perovskites BaInxZr1-xO3-x/2 (x = 0.10-0.75) over the temperature range -160 to 350 degrees C. Upon increasing temperature from -160 to 30 degrees C, we show that there is a redistribution of protons from nonsymmetrical structural configurations, such as Zr-OH-In and Zr-OH-Zr-vacancy, where the degree of hydrogen bonding between the protons and neighboring oxygens is strong, to symmetrical configurations, such as Zr-OH-Zr and In-OH-In, where hydrogen bonding is weaker. Spectra measured at elevated temperatures, 30-350 degrees C, indicate preferential desorption of protons in sites where the degree of hydrogen bonding is strong, and show that the materials gradually dehydrate with increasing temperature. The dehydration rate is found to be highest in the temperature range 275-325 degrees C. Furthermore, the spectroscopic results indicate that strong hydrogen bonding, caused by dopant-induced short-range structural distortions, is favorable for high proton mobility and that the rate-limiting step in the conduction mechanism is the proton transfer between neighboring oxygens.
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