High pressure structural phase transitions in Ho: Eu2O3

Irshad, K. A.; Shekar, N. V. Chandra; Srihari, Velaga; Pandey, K. K.; Kalavathi, S.

doi:10.1016/j.jallcom.2017.07.224

Cited by 21 publications

(16 citation statements)

References 30 publications

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“…A phase transition from cubic to hexagonal structure is observed at 5.3 GPa and the high pressure phase is stable up to 28.1 GPa. These results are in good agreement with the available reports on Eu 2 O 3 8 . It is known that, the structure and phase transitions in the RES are highly influenced by their cationic radii 6,8,11,14,22 .…”

Section: Structural Phase Transitions In (Eu 1−x Lasupporting

confidence: 93%

“…1 the HPXRD patterns collected for at different pressure steps are shown. Typically, the structural transitions either from C B or C A is characterized by the origin of a new peak near the cubic 123 and 222 peak 8 . For , the diffraction pattern doesn’t show any signature of structural phase transition till 5.8 GPa.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, the sesquioxides of medium cation size follows a direct C A transition at high pressures. Though these transitions are well known, a systematic study revealing the cation size dependent structural phase transitions has been primarily investigated on (Eu 1− x Ho x ) 2 O 3 solid solutions by our own group 8 . This study was carried out by keeping the aim to investigate the structural stability of RES as a function of both cation size and pressure by considering the solid solutions of RES having similar structure and small difference in their cation size.…”

Section: Introductionmentioning

confidence: 99%

“…by using cation size as a tuning parameter [7][8][9][10] . The structural stability and phase transition as a function of cation size have been studied by many groups and is available in the literature [11][12][13][14] .…”

mentioning

confidence: 99%

“…This study was carried out by keeping the aim to investigate the structural stability of RES as a function of both cation size and pressure by considering the solid solutions of RES having similar structure and small difference in their cation size. The high pressure structural stability of cubic phase of (Eu 1−x Ho x ) 2 O 3 solid solutions has been thoroughly studied and a pressure concentration phase diagram has been established recently 8 . In fact, this is the first experimental phase diagram delineating the phase boundaries of the high pressure phases (monoclinic and hexagonal) of these oxides as a function of cation size.…”

mentioning

confidence: 99%

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Structural phase transition, equation of state and phase diagram of functional rare earth sesquioxide ceramics (Eu1−xLax)2O3

Irshad

Srihari

Kalavathi

et al. 2020

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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...

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