Single-crystal X-ray diffraction study of SrGeO3 high-pressure perovskite phase at 100 K

Nakatsuka, Akihiko; Arima, Hiroshi; Ohtaka, Osamu; Fujiwara, Keiko; Yoshiasa, Akira

doi:10.1088/1742-6596/950/4/042015

Cited by 3 publications

(6 citation statements)

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“…5). This result confirms the prediction of Nakatsuka et al (2017), who inferred the temperature dependence of the MSD of the O atom by comparison between previously reported refinement results at 296 and 100 K. Such peculiar temperature dependence of the O atom will originate in strong interactions with Figure 6. Unit cell of the SrGeO 3 perovskite at 298 K with displacement ellipsoids drawn at a probability level of 80%.…”

Section: Temperature Dependence Of Mean-square Displacements (Msds) Osupporting

confidence: 92%

“…As reported in our previous study (Nakatsuka et al, 2015a), the sixfold-coordinated Ge-O bond in the SrGeO 3 perovskite has a high covalency comparable to those of the fourfold-coordinated Si-O bonds in silicates of approximately 50%. As a supportive observation, in our recent study (Nakatsuka et al, 2017), we successfully detected the residual electron density peaks originating in the bonding electrons of the Ge-O bonds in the difference Fourier map at 100 K. The peculiar temperature dependence of the thermal vibration of the O atom observed in Figure 5 can be attributed to the high covalency of the Ge-O bond.…”

Section: Temperature Dependence Of Mean-square Displacements (Msds) Osupporting

confidence: 75%

“…1) and is important in earth science as a potentially good low-pressure analog of the CaSiO 3 cubic perovskite, a constituent mineral in the Earth's lower mantle. Recently, we successfully synthesized single-crystals of the SrGeO 3 perovskite phase at high-pressure and -temperature conditions and carried out single-crystal X-ray diffraction (XRD) analyses at 296 K (Nakatsuka et al, 2015a) and 100 K (Nakatsuka et al, 2017). A comparison of the structure-refinement results between the two temperatures showed that the high covalency of the Ge-O bond largely restricts the thermal vibration of the O atom and can have a large influence on its temperature dependence.…”

Section: Introductionmentioning

confidence: 99%

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Variable–temperature single–crystal X–ray diffraction study of SrGeO3 high–pressure perovskite phase

Nakatsuka

Yoshiasa

Fujiwara

et al. 2018

Journal of Mineralogical and Petrological Sciences

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Single-crystal X-ray diffraction analysis of a high-pressure cubic perovskite SrGeO 3 was conducted for a temperature range of 100 to 473 K. The crystal structure begins to deteriorate at a temperature higher than 323 K and completely amorphizes by 448 K. Structure refinements in a range of 100 to 323 K show that the displacement ellipsoid of the O atom is considerably suppressed in the direction of the Ge-O bond and that its mean square displacement (MSD) in this direction is almost temperature-independent. In contrast, that in the direction perpendicular to the bond largely increases with the temperature. The Debye temperatures for each constituent atom were determined by applying the Debye model to the temperature dependence of its MSDs. The one-particle potential (OPP) coefficient evaluated from the resulting Debye temperature of the Ge atom is significantly larger than those of the Sr and O atoms. Moreover, the OPP coefficients of the O atom are significantly larger in the direction of the Ge-O bond than in the directions perpendicular to the bond. These results are concordant with our previous finding that the Ge-O bond is largely covalent. The high covalency can have a large influence on the temperature dependence of the thermal vibration of the O atom.

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Section: Temperature Dependence Of Mean-square Displacements (Msds) Osupporting

confidence: 92%

Section: Temperature Dependence Of Mean-square Displacements (Msds) Osupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

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Variable–temperature single–crystal X–ray diffraction study of SrGeO3 high–pressure perovskite phase

Nakatsuka

Yoshiasa

Fujiwara

et al. 2018

Journal of Mineralogical and Petrological Sciences

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“…Since then, the Sr-Ge-O system has also been of interest in the field of materials science. We recently reported the single-crystal growth of SrGeO 3 perovskite and its structural study Nakatsuka et al, 2016). We noticed that in this crystal-growth experiment under high pressure and high temperature, single crystals of the unknown phase with the composition SrGe 2 O 5 co-existed in the recovered sample together with the perovskite single crystals.…”

Section: Introductionmentioning

confidence: 87%

“…Meanwhile, germanates have frequently been employed as model substances for the corresponding silicates (e.g. Nakatsuka et al, 2005Nakatsuka et al, , 2016Nakatsuka, Kuribayashi et al, 2015;Koganemaru et al, 2013) because they exhibit similar phase transformations to those of silicates at lower pressures. Phase and structural studies of germanates have thus provided important insights into phase transformations of silicate minerals in the Earth's interior.…”

Section: Introductionmentioning

confidence: 99%

A new high-pressure strontium germanate, SrGe₂O₅

Nakatsuka

Sugiyama

Ohkawa

et al. 2016

Acta Crystallogr C Struct Chem

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The Sr-Ge-O system has an earth-scientific importance as a potentially good low-pressure analog of the Ca-Si-O system, one of the major components in the constituent minerals of the Earth's crust and mantle. However, it is one of the germanate systems that has not yet been fully examined in the phase relations and structural properties. The recent findings that the SrGeO high-pressure perovskite phase is the first Ge-based transparent electronic conductor make the Sr-Ge-O system interesting in the field of materials science. In the present study, we have revealed the existence of a new high-pressure strontium germanate, SrGeO. Single crystals of this compound crystallized as a co-existent phase with SrGeO perovskite single crystals in the sample recovered in the compression experiment of SrGeO pseudowollastonite conducted at 6 GPa and 1223 K. The crystal structure consists of germanium-oxygen framework layers stacked along [001], with Sr atoms located at the 12-coordinated cuboctahedral site; the layers are formed by the corner linkages between GeO octahedra and between GeO octahedra and GeO tetrahedra. The present SrGeO is thus isostructural with the high-pressure phases of SrSiO and BaGeO. Comparison of these three compounds leads to the conclusion that the structural responses of the GeO and GeO polyhedra to cation substitution at the Sr site are much less than that of the SrO cuboctahedron to cation substitution at the Ge sites. Such a difference in the structural response is closely related to the bonding nature.

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Prospects for high carrier mobility in the cubic germanates

Rowberg¹,

Krishnaswamy²,

Walle³

2020

Semicond. Sci. Technol.

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High-mobility wide-band-gap oxides are essential materials for device applications in high-frequency and power electronics. We use first-principles calculations to evaluate the potential of two cubic perovskite germanates, SrGeO 3 and BaGeO 3 , for these applications. We find their effective masses to be small, both for electrons and holes. The prospect of p-type conductivity renders the germanates attractive for complementary metal-oxide-semiconductor technology. We calculate the electron drift mobility in SrGeO 3 to lie between 400 and 500 cm 2 V −1 s −1 for a range of accessible carrier concentrations; this mobility is as much as 50% larger than in BaSnO 3 , which has the highest room-temperature electron mobility among perovskite oxides. Our results suggest that the germanates hold promise for high-mobility electronic applications.

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Single-crystal X-ray diffraction study of SrGeO₃ high-pressure perovskite phase at 100 K

Cited by 3 publications

References 9 publications

Variable–temperature single–crystal X–ray diffraction study of SrGeO<sub>3</sub> high–pressure perovskite phase

Variable–temperature single–crystal X–ray diffraction study of SrGeO<sub>3</sub> high–pressure perovskite phase

A new high-pressure strontium germanate, SrGe₂O₅

Prospects for high carrier mobility in the cubic germanates

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Single-crystal X-ray diffraction study of SrGeO3 high-pressure perovskite phase at 100 K

Cited by 3 publications

References 9 publications

Variable–temperature single–crystal X–ray diffraction study of SrGeO<sub>3</sub> high–pressure perovskite phase

Variable–temperature single–crystal X–ray diffraction study of SrGeO<sub>3</sub> high–pressure perovskite phase

A new high-pressure strontium germanate, SrGe2O5

Prospects for high carrier mobility in the cubic germanates

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Product

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Single-crystal X-ray diffraction study of SrGeO₃ high-pressure perovskite phase at 100 K

A new high-pressure strontium germanate, SrGe₂O₅