Phase changes and thermodynamic properties of CaTiO3. Spectroscopic data, vibrational modelling and some insights on the properties of MgSiO3 perovskite

Gillet, Philippe; Guyot, François; Price, G. D.; Tournerie, Benoît; Cleac'h, Andrée Le

doi:10.1007/bf00200118

Cited by 79 publications

(65 citation statements)

References 49 publications

(84 reference statements)

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“…However, Ti 3 O 5 is also a substance which undergoes phase transitions of crystal structures during heating. A transition from monoclinic to orthorhombic phases has been seen at a temperature of 514 K (Onoda 1998 (Gillet 1993) similarly to other Ti-compounds.…”

Section: A4 Ti 3 Omentioning

confidence: 59%

Morphological effects on IR band profiles

Tamanai¹,

Mutschke²,

Blum

et al. 2009

A&A

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Aims. To trace the source of the unique 13, 19.5, and 28 μm emission features in the spectra of oxygen-rich circumstellar shells around AGB stars, we have compared dust extinction spectra obtained by aerosol measurements. Methods. We have measured the extinction spectra for 19 oxide powder samples of eight different types, such as Ti-compounds (TiO, TiO 2 , Ti 2 O 3 , Ti 3 O 5 , Al 2 TiO 5 , CaTiO 3 ), α-, γ-, χ-δ-κ-Al 2 O 3 , and MgAl 2 O 4 in the infrared region (10-50 μm) paying special attention to the morphological (size, shape, and agglomeration) effects and the differences in crystal structure. Results. Anatase (TiO 2 ) particles with rounded edges are the possible 13, 19.5 and 28 μm band carriers as the main contributor in the spectra of AGB stars, and spherically shaped nano-sized spinel and Al 2 TiO 5 dust grains are possibly associated with the anatase, enhancing the prominence of the 13 μm feature and providing additional features at 28 μm. The extinction data sets obtained by the aerosol and CsI pellet measurements have been made available for public use at http://elbe.astro.uni-jena.de.

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Section: A4 Ti 3 Omentioning

confidence: 59%

Morphological effects on IR band profiles

Tamanai¹,

Mutschke²,

Blum

et al. 2009

A&A

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“…7(c)) cannot be associated with a transition to such a phase. Firstly, the group-theoretical calculation for the Pnma phase yields Γ Raman,Pnma =7A g +7B 1g +5B 2g +5B 3g , 42 i.e., 24 Raman-active modes, of which some should appear for wavenumbers <400 cm -1 . 22 In the present observation, no extra modes appeared in this range.…”

Section: Discussionmentioning

confidence: 99%

Structure and properties of Fe-modified Na0.5Bi0.5TiO3at ambient

et al. 2012

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Sodium bismuth titanate (NBT) ceramics are among the most promising lead-free materials for piezoelectric applications. This work reports the crystal structure and phase evolution of NBT and Fe-modified NBT (from 0-2 at% Fe) using synchrotron X-ray diffraction and Raman spectroscopy, both at ambient and elevated temperatures. The crystallographic results are discussed with reference to permittivity and piezoelectric thermal depolarization measurements of the same compositions. Changes in the depolarization temperature due to Fe substitution were detected by Raman spectroscopy, and were found to correlate closely with depolarization temperatures obtained from converse piezoelectric coefficient and permittivity measured in situ. The depolarization temperatures obtained from direct piezoelectric coefficient measured ex situ as well as the phase transition temperatures obtained from synchrotron X-ray diffraction were found to be at higher temperatures. The mechanisms underlying the relationship between permittivity and piezoelectric depolarization to structural transitions observed in Raman spectroscopy and X-ray diffraction are discussed.

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“…Figure 2 shows the transmission spectrum for each cloud condensate in Table 1 computed for the atmosphere of HD 189733b given a condensate grain size of 0.1 µm and abundances 1× solar. We plot the spectrum in units of scale height, H, such that the transmission spectra of different exoplanets will appear very similar, as z/H is only weakly dependent upon specific values of R p or g. The different condensates have been separated into groups of their primary diatomic bond to highlight Glassgold & Graham (2008); (b) Lehnert et al (2002); (c) Saniger (1995); (d) Gillet et al (1993); (e) Batsanov & Derbeneva (1969); ( f ) Kröger & Meyer (1954); (g) Rice & Klemperer (2004).…”

Section: Condensate Abundancementioning

confidence: 99%

Transmission spectral properties of clouds for hot Jupiter exoplanets

Wakeford

Sing

2015

A&A

181

205

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Clouds play an important role in the atmospheres of planetary bodies. It is expected that, like all the planetary bodies in our solar system, exoplanet atmospheres will also have substantial cloud coverage, and evidence is mounting for clouds in a number of hot Jupiters. To better characterise planetary atmospheres, we need to consider the effects these clouds will have on the observed broadband transmission spectra. Here we examine the expected cloud condensate species for hot Jupiter exoplanets and the effects of various grain sizes and distributions on the resulting transmission spectra from the optical to infrared, which can be used as a broad framework when interpreting exoplanet spectra. We note that significant infrared absorption features appear in the computed transmission spectrum, the result of vibrational modes between the key species in each condensate, which can potentially be very constraining. While it may be hard to differentiate between individual condensates in the broad transmission spectra, it may be possible to discern different vibrational bonds, which can distinguish between cloud formation scenarios, such as condensate clouds or photochemically generated species. Vibrational mode features are shown to be prominent when the clouds are composed of small sub-micron sized particles and can be associated with an accompanying optical scattering slope. These infrared features have potential implications for future exoplanetary atmosphere studies conducted with JWST, where such vibrational modes distinguishing condensate species can be probed at longer wavelengths.

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Phase changes and thermodynamic properties of CaTiO3. Spectroscopic data, vibrational modelling and some insights on the properties of MgSiO3 perovskite

Cited by 79 publications

References 49 publications

Morphological effects on IR band profiles

Morphological effects on IR band profiles

Structure and properties of Fe-modified Na0.5Bi0.5TiO3at ambient

Transmission spectral properties of clouds for hot Jupiter exoplanets

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