Heat Capacity of the R2Ge2O7 (R = Pr–Lu, Y) Rare-Earth Germanates

Денисова, Л. Т.; Kargin, Yu. F.; Belousova, N. V.; Irtyugo, L. A.; Денисов, В. М.; Белецкий, В. В.

doi:10.1134/s0020168519090024

Cited by 6 publications

(5 citation statements)

References 27 publications

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“…The case of germanates is much more complex, and the cubic pyrochlore phase can only be obtained using high‐pressure synthesis. At ambient pressure, the structure is tetragonal (space group: P 4 1 2 1 2) from Tb to Yb, 29 triclinic for La, Pr, and Nd, and can be triclinic, hexagonal, or tetragonal for Gd, Eu, and Sm 29,30 …”

Section: Resultsmentioning

confidence: 99%

“…Structures adopted for the RE 2 B 2 O 7 depending on the nature of rare earth (RE = La–Yb) and of the B cation (B = Ge, Ti, Sn, Zr, and Hf) 9,27–30 . *In this figure, avg.…”

Section: Resultsmentioning

confidence: 99%

“…9,28 The case of germanates is much more complex, and the cubic pyrochlore phase can only be obtained using high-pressure synthesis. At ambient pressure, the structure is tetragonal (space group: P4 1 2 1 2) from Tb to Yb, 29 triclinic for La, Pr, and Nd, and can be triclinic, hexagonal, or tetragonal for Gd, Eu, and Sm. 29,30 Two different competing evolutions emerge from Figure 3: From La to Yb, the enthalpic cost due to the addition of germanium decreases (in the meantime as the r A /r B decreases), whereas the enthalpic cost due to forcing zirconium and hafnium to be in an ordered structure is increasing (the RE 2 Zr 2 O 7 or RE 2 Hf 2 O 7 compounds go from an ordered pyrochlore structure to a defect fluorite, with an intermediate region where a transition from the pyrochlore to the fluorite structure is observed at high temperature).…”

Section: A-site Substitution In Re 2 (Tizrhfgesn) 2 Omentioning

confidence: 99%

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Investigation of the chemical versatility in high‐entropy pyrochlores

et al. 2022

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This article reports on the exploration of the chemical versatility of entropy‐stabilized pyrochlores (A2B2O7) with large chemical disorder introduced on the B site, as well as the study of isovalent and aliovalent substitution on the B site and of Ca2+‐doping on the A site. Among all the 20 new compounds obtained in this study, 8 are entropy‐stabilized: RE2(TiZrHfGeSn)2 (with RE = Gd–Ho and Y), Pr2(TiZrHfScNb)2O7, and RE2(TiGeSnAlNb)2O7 (with RE = Er and Y). Moreover, some physical properties (magnetic, electrical, thermal, and optical properties) of these high‐entropy pyrochlores have been screened, and some of them could be potentially interesting for applications. For example, we observed low thermal diffusivity values (between 0.4 and 0.7 m2 s−1) making them interesting for thermal barrier coating or tunable optical bandgaps in the visible region that could make them appealing as photocatalysts or in optical applications. Furthermore, single‐phased compounds were obtained for almost all the rare earths (REs) on the A site. Therefore, when five nonmagnetic cations are used for the B site, it enables to study the magnetic properties and, more specifically, the influence of the local chemical and structural disorder on the exotic ground states observed in monocationic RE pyrochlores.

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Section: Resultsmentioning

confidence: 99%

“…Structures adopted for the RE 2 B 2 O 7 depending on the nature of rare earth (RE = La–Yb) and of the B cation (B = Ge, Ti, Sn, Zr, and Hf) 9,27–30 . *In this figure, avg.…”

Section: Resultsmentioning

confidence: 99%

Section: A-site Substitution In Re 2 (Tizrhfgesn) 2 Omentioning

confidence: 99%

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Investigation of the chemical versatility in high‐entropy pyrochlores

et al. 2022

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“…Они кристаллизуются в разных структурных типах [1,6]. Кристаллическая структура этих соединений хорошо изучена [2,7], однако для ряда редкоземельных германатов отсутствуют экспериментальные данные по фононным спектрам и упругим постоянным. Редкоземельные германаты имеют потенциальное применение в качестве сцинтилляторов [8], иттриевый германат Y 2 Ge 2 O 7 используется как матрица для допирования редкоземельными ионами [9,10].…”

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Структура и динамика решетки тетрагональных германатов R-=SUB=-2-=/SUB=-Ge-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- (R=Tb-Lu, Y): ab initio расчет

Рюмшин¹,

Chernyshev²

2021

Физика Твердого Тела

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Within the framework of density functional theory, an ab initio calculation was carried out to study the crystal structure, phonon spectrum and elastic constants of a series of rare-earth germanates, including yttrium germanate R2Ge2O7 (R = Tb-Lu, Y) with tetragonal structure. The frequencies and types of fundamental vibrations as well as the intensities of the IR and Raman modes were determined. The degree of participation of ions in each mode was determined from the analysis of the displacement vectors obtained from the ab initio calculation. The calculations were performed for the first time. The corresponding experimental data for the entire series, with the exception of the IR and Raman spectra of yttrium germanate, are absent. The calculations made it possible to interpret and supplement available in the scientific articles results of measurements of the IR and Raman spectra of yttrium germanate Y2Ge2O7.

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“…They are crystallized into different structure types [1,6]. The crystal structure of these compounds has been thoroughly studied [2,7]; however, there are no experimental data on the phonon spectra and elastic constants for series rare-earth germanates. Rareearth germanates are promising as scintillators [8]; yttrium germanate Y 2 Ge 2 O 7 is used as a matrix for doping by rare-earth ions [9,10].…”

mentioning

confidence: 99%

Structure and Dynamics of a Lattice of Tetragonal Germanates R2Ge2O7 (R = Tb–Lu, Y): Ab Initio Calculation

Ryumshin

Chernyshev

2021

Phys. Solid State

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The crystal structure, phonon spectrum, and elastic constants of a series of rare-earth germanates (including yttrium germanate R 2 Ge 2 O 7 (R = Tb-Lu, Y)) with a tetragonal structure have been ab initio calculated within the density functional theory. The frequencies and types of fundamental vibrations and the intensities of IR and Raman modes are determined. The degrees of participation of ions in each mode are determined by analyzing the displacement vectors obtained as a result of the ab initio calculations. The calculations have been performed for the first time; there are no corresponding experimental data for the entire series of compounds (except for the IR and Raman spectra of yttrium germanate). The performed calculations made it possible to interpret and supplement the known data in the literature on IR and Raman spectra of yttrium germanate Y 2 Ge 2 O 7 .

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Heat Capacity of the R2Ge2O7 (R = Pr–Lu, Y) Rare-Earth Germanates

Cited by 6 publications

References 27 publications

Investigation of the chemical versatility in high‐entropy pyrochlores

Investigation of the chemical versatility in high‐entropy pyrochlores

Структура и динамика решетки тетрагональных германатов R-=SUB=-2-=/SUB=-Ge-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- (R=Tb-Lu, Y): ab initio расчет

Structure and Dynamics of a Lattice of Tetragonal Germanates R2Ge2O7 (R = Tb–Lu, Y): Ab Initio Calculation

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