Abstract:The structural stability of hexagonal Nd2O3 under pressure has been investigated by in situ synchrotron angle dispersive x-ray diffraction and Raman spectroscopy up to 53.1 GPa and 37.0 GPa, respectively. Rietveld analysis of the x-ray diffraction data indicate that the hexagonal Nd2O3 undergoes an isostructural phase transition in the pressure range from 10.2 to 20.3 GPa, accompanied by anomalous lattice compressibility and pressure-volume curve. A third-order Birch-Murnaghan fit based on the observed Pressur… Show more
“…A-type Nd 2 O 3 has been observed to suffer a reversible PT above 27 GPa towards a monoclinic s.g. P2/m phase [67]. However, other work has suggested a 1st-order isostructural PT above 10 GPa [68]. This behavior is in contrast with that of Ce 2 O 3 , which seems to be stable in the A-type phase up to 70 GPa.…”
Section: Introductionmentioning
confidence: 78%
“…Finally, as regards the B→A PT, the pressure of the transition once again increases along the lanthanide series with the increase in atomic number or the decrease in the ionic radius. As observed, no experimental data for the B→A PT 4.0 XRD N2, Ar [11] 4.2 2.5 XRD Silicon Oil [45] The HP behavior of A-type compounds has been studied in Nd2O3 [67,68], Ce2O3 [69], and La2O3 [11]. A-type Nd2O3 has been observed to suffer a reversible PT above 27 GPa towards a monoclinic s.g. P2/m phase [67].…”
Section: Compmentioning
confidence: 99%
“…stands for polyethylene glycol. The HP behavior of A-type compounds has been studied in Nd 2 O 3 [67,68], Ce 2 O 3 [69], and La 2 O 3 [11]. A-type Nd 2 O 3 has been observed to suffer a reversible PT above 27 GPa towards a monoclinic s.g. P2/m phase [67].…”
Pressure is an important thermodynamic parameter, allowing the increase of matter density by reducing interatomic distances that result in a change of interatomic interactions. In this context, the long range in which pressure can be changed (over six orders of magnitude with respect to room pressure) may induce structural changes at a much larger extent than those found by changing temperature or chemical composition. In this article, we review the pressure-induced phase transitions of most sesquioxides, i.e., A2O3 compounds. Sesquioxides constitute a big subfamily of ABO3 compounds, due to their large diversity of chemical compositions. They are very important for Earth and Materials Sciences, thanks to their presence in our planet’s crust and mantle, and their wide variety of technological applications. Recent discoveries, hot spots, controversial questions, and future directions of research are highlighted.
“…A-type Nd 2 O 3 has been observed to suffer a reversible PT above 27 GPa towards a monoclinic s.g. P2/m phase [67]. However, other work has suggested a 1st-order isostructural PT above 10 GPa [68]. This behavior is in contrast with that of Ce 2 O 3 , which seems to be stable in the A-type phase up to 70 GPa.…”
Section: Introductionmentioning
confidence: 78%
“…Finally, as regards the B→A PT, the pressure of the transition once again increases along the lanthanide series with the increase in atomic number or the decrease in the ionic radius. As observed, no experimental data for the B→A PT 4.0 XRD N2, Ar [11] 4.2 2.5 XRD Silicon Oil [45] The HP behavior of A-type compounds has been studied in Nd2O3 [67,68], Ce2O3 [69], and La2O3 [11]. A-type Nd2O3 has been observed to suffer a reversible PT above 27 GPa towards a monoclinic s.g. P2/m phase [67].…”
Section: Compmentioning
confidence: 99%
“…stands for polyethylene glycol. The HP behavior of A-type compounds has been studied in Nd 2 O 3 [67,68], Ce 2 O 3 [69], and La 2 O 3 [11]. A-type Nd 2 O 3 has been observed to suffer a reversible PT above 27 GPa towards a monoclinic s.g. P2/m phase [67].…”
Pressure is an important thermodynamic parameter, allowing the increase of matter density by reducing interatomic distances that result in a change of interatomic interactions. In this context, the long range in which pressure can be changed (over six orders of magnitude with respect to room pressure) may induce structural changes at a much larger extent than those found by changing temperature or chemical composition. In this article, we review the pressure-induced phase transitions of most sesquioxides, i.e., A2O3 compounds. Sesquioxides constitute a big subfamily of ABO3 compounds, due to their large diversity of chemical compositions. They are very important for Earth and Materials Sciences, thanks to their presence in our planet’s crust and mantle, and their wide variety of technological applications. Recent discoveries, hot spots, controversial questions, and future directions of research are highlighted.
“…To the best of our knowledge, there is no Raman spectroscopy data for the trigonal structure of Eu 2 O 3 , but the Raman modes measured for other A-type sesquioxides are arranged just as in our calculations: two bending vibrations of low-frequency between 100 and 200 cm –1 and two stretching vibrations occurring at a higher frequency region between 400 and 450 cm –1 . 9 , 30 , 31 Under pressure, the Raman modes of the trigonal structure shift to higher frequencies. In Table 1 , the frequencies of the zone-center modes calculated for the trigonal structure at p = 0 and 6 GPa are presented.…”
Using the density
functional theory, we study the structural and
lattice dynamical properties of europium sesquioxide (Eu
2
O
3
) in the cubic, trigonal, and monoclinic phases. The
obtained lattice parameters and energies of the Raman modes show a
good agreement with the available experimental data. The Eu-partial
phonon density of states calculated for the cubic structure is compared
with the nuclear inelastic scattering data obtained from a 20 nm thick
Eu
2
O
3
film deposited on a YSZ substrate. A small
shift of the experimental spectrum to higher energies results from
a compressive strain induced by the substrate. On the basis of lattice
and phonon properties, we analyze the mechanisms of structural transitions
between different phases of Eu
2
O
3
.
“…This signifies that, the monoclinic phase is completely transformed to the hexagonal structure well below this pressure. Also, it has been observed that, the 100 peak of the hexagonal structure of and 0.6 hardly shift with an increase of pressure in the ~ 10–22 GPa pressure regime, indicative of the presence of anomalous lattice compressibility, similar to the one in the hexagonal structure of pristine La 2 O 3 , Nd 2 O 3 and Eu 2 O 3 15 , 17 , 18 . Figure 1 HPXRD pattern of x = 0.3–0.6 representing the high pressure behavior of (Eu 1− x La x ) 2 O 3 .…”
the intriguing functional nature of ceramics containing rare earth sesquioxide (ReS) is associated with the type of polymorphic structure they crystallize into. they prefer to be in the cubic, monoclinic or hexagonal structure in the increasing order of cation size, R Re. Since the functional properties of these ceramics varies with R Re , temperature and pressure, a systematic investigation delineating the cation size effect is indispensable. In the present work we report the structural stability and compressibility behaviour of the ReS ceramics, (eu 1−x La x) 2 o 3 , of ReSs with dissimilar structure and significant difference in cationic radii. The selected compositions of (Eu 1−x La x) 2 o 3 have been studied using the in-situ high pressure synchrotron X-ray diffraction and the structural parameters obtained through Rietveld refinement. The cubic structure, which is stable for 0.95 Å ≤ R Re < 0.98 Å at ambient temperature and pressure (Atp), prefers a cubic to hexagonal transition at high pressures. the biphasic region of cubic and monoclinic structure, which is stable for 0.98 Å ≤ R Re < 1.025 Å at ATP, prefers a cubic/monoclinic to hexagonal transition at high pressures. further, in the biphasic region of monoclinic and hexagonal structure, observed for 1.025 Å ≤R Re < 1.055 Å, the monoclinic phase is found to be progressing towards the hexagonal phase with increasing pressure. the pure hexagonal phase obtained for 1.055 Å ≤ R Re ≤ 1.10 Å is found to be structurally stable at high pressures. The bulk moduli are obtained from the Birch-Murnaghan equation of state fit to the compressibility data and its dependance on the cation size is discussed. The microstrain induced by the difference in cation size causes an internal pressure in the crystal structure leading to a reduction in the bulk modulus of x = 0.2 and 0.6. A pressure-concentration (P-x) phase diagram upto a pressure of 25 GPa is constructed for (eu 1−x La x) 2 o 3. this would provide an insight to the fundamental and technological aspects of these materials and the ReSs in general. Rare earth sesquioxides (RESs) are promising candidate materials for a wide variety of applications in many of the technologically important fields. They are useful candidates as scintillating materials, phosphor materials, wave guides, superconducting materials and many others 1-4. These oxides are known to exist in three different polymorphic structures at ambient conditions. They are designated as C-type (cubic), B-type (monoclinic) and A-type (hexagonal) structure 5,6. The C-type structure belongs to the cubic crystal system crystallizing in the Ia3 space group (SG). The rare earth (RE) cations in this structure occupy two different Wyckoff 's site 8b and 24d and are octahedrally coordinated with the oxygen atoms. The B-type structure with SG C2/m is shown by the medium cation sized RES (Sm 2 O 3 , Eu 2 O 3 and Gd 2 O 3) and the cations in this structure occupy four 4i Wyckoff 's sites and the oxygen occupies the three 4i Wyckoff 's sites. Here, the cations are in six...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
