A lattice dynamical investigation of the Raman and the infrared frequencies of the cubic A2Hf2O7 pyrochlores

Gupta, H.C.; Brown, Suree; Rani, Nisha; Gohel, V. B.

doi:10.1016/s0022-3697(01)00151-2

Cited by 33 publications

(18 citation statements)

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“…Figure 2a shows the transmission and reflection spectra of La 2 Zr 2 O 7 bulk samples. Seven phonon modes are observed, which is consistent with the previous experimental result and theoretical group analysis 14. The infrared transmission spectra of the La 2 Zr 2 O 7 thin films are shown in Fig.…”

Section: Resultssupporting

confidence: 90%

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Infrared phonon modes and dielectric properties of La₂Zr₂O₇: Comparing thin film to bulk material

Cheng

et al. 2011

Physica Status Solidi (b)

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The infrared phonon modes and dielectric constants of bulk and thin film of La 2 Zr 2 O 7 are studies by infrared spectroscopy. The infrared response of the La 2 Zr 2 O 7 bulk sample is determined by seven infrared phonon modes. The obtained static dielectric constant is 22.8 and the largest contribution is from the phonon modes at 213.7 and 352.7 cm À1. Compared to the bulk sample, the obtained dielectric constant of the La 2 Zr 2 O 7 thin film shows an obvious decrease. The loss of the dielectric constant is due to the absence and weakness of some phonon modes in the thin film, even though it still preserves two important modes, mentioned above. The result indicates that the disorder in the La 2 Zr 2 O 7 thin film has an important influence on the dielectric property.

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Section: Resultssupporting

confidence: 90%

“…Out of these 26 normal modes, only 7F 1u modes are infrared active modes and the remaining F 1u mode is an acoustic mode 13. The A 1g, E g, 4F 2g modes are Raman active 14, 15.…”

Section: Experiments and Data Analysismentioning

confidence: 99%

Infrared phonon modes and dielectric properties of La₂Zr₂O₇: Comparing thin film to bulk material

Cheng

et al. 2011

Physica Status Solidi (b)

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“…The figure depicts the room-temperature ͑RT͒ parallel polarization spectra of the rare earth titanates and the corresponding modes. The assignment of the mode symmetries is based on comparison with assignments in previous works on these [57][58][59][60][61][62] and related [62][63][64][65][66][67] compounds ͑see Table II͒, on aforementioned measurements ͑not shown͒ of the angular dependence of mode intensities and on the temperature dependence of the modes ͑vide infra͒.…”

Section: A Magnetic Measurementsmentioning

confidence: 99%

Phonon and crystal field excitations in geometrically frustrated rare earth titanates

et al. 2008

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. are used for characterization, while Raman spectroscopy and terahertz time domain spectroscopy are employed to probe the excitations in the materials. The lattice excitations are found to be analogous across the compounds over the whole temperature range investigated ͑295-4 K͒. The resulting full phononic characterization of the R 2 Ti 2 O 7 pyrochlore structure is then used to identify crystal field excitations observed in the materials. Several crystal field excitations have been observed in Tb 2 Ti 2 O 7 in Raman spectroscopy, among which all of the previously reported excitations. The presence of additional crystal field excitations, however, suggests the presence of two inequivalent Tb 3+ sites in the low-temperature structure. Furthermore, the crystal field level at approximately 13 cm −1 is found to be both Raman and dipole active, indicating broken inversion symmetry in the system and thus undermining its current symmetry interpretation. In addition, evidence is found for a significant crystal field-phonon coupling in Tb 2 Ti 2 O 7 . The additional crystal field information on Tb 2 Ti 2 O 7 adds to the recent discussion on the low temperature symmetry of this system and may serve to improve its theoretical understanding.

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“…11 By establishing a linear trend between disorder energy and temperature, Stanek and Grimes 15 compared disorder energies to phase diagram data, and predicted the possibilities of Dy 2 Hf 2 O 7 , Ho 2 Hf 2 O 7 , and Er 2 Hf 2 O 7 formation. 6,13,[23][24][25] In this work, first-principles calculations based on density functional theory ͑DFT͒ have been performed on A 2 Hf 2 O 7 ͑A = Dy, Ho, Er͒ within the framework of generalized gradient approximation ͑GGA͒. 6,13,[23][24][25] In this work, first-principles calculations based on density functional theory ͑DFT͒ have been performed on A 2 Hf 2 O 7 ͑A = Dy, Ho, Er͒ within the framework of generalized gradient approximation ͑GGA͒.…”

Section: First-principles Study Of Structural and Energetic Propertiementioning

confidence: 99%

First-principles study of structural and energetic properties of A2Hf2O7 (A=Dy, Ho, Er) compounds

Gao

2008

Journal of Applied Physics

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The structural and energetic properties of A 2 Hf 2 O 7 ͑A = Dy, Ho, Er͒ compounds have been investigated by means of ab initio total energy calculations. For Er 2 Hf 2 O 7 the defect fluorite structure is predicted to be more stable than pyrochlore structure, agreeing well with previous experimental ͓J. Inorg. Nucl. Chem. 31, 2367 ͑1969͒; J. Less Common Met. 14, 435 ͑1968͔͒ and theoretical ͓J. Am. Ceram. Soc. 85, 2139 ͑2002͔͒ investigations. In contrast to Er 2 Hf 2 O 7 pyrochlore, Dy 2 Hf 2 O 7 and Ho 2 Hf 2 O 7 prefer pyrochlore structures, which is consistent with the recent experimental observations of Dy 2 Hf 2 O 7 compound ͓J. Solid State Chem. 179, 1990 ͑2006͔͒.

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A lattice dynamical investigation of the Raman and the infrared frequencies of the cubic A2Hf2O7 pyrochlores

Cited by 33 publications

References 3 publications

Infrared phonon modes and dielectric properties of La₂Zr₂O₇: Comparing thin film to bulk material

Infrared phonon modes and dielectric properties of La₂Zr₂O₇: Comparing thin film to bulk material

Phonon and crystal field excitations in geometrically frustrated rare earth titanates

First-principles study of structural and energetic properties of A2Hf2O7 (A=Dy, Ho, Er) compounds

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A lattice dynamical investigation of the Raman and the infrared frequencies of the cubic A2Hf2O7 pyrochlores

Cited by 33 publications

References 3 publications

Infrared phonon modes and dielectric properties of La2Zr2O7: Comparing thin film to bulk material

Infrared phonon modes and dielectric properties of La2Zr2O7: Comparing thin film to bulk material

Phonon and crystal field excitations in geometrically frustrated rare earth titanates

First-principles study of structural and energetic properties of A2Hf2O7 (A=Dy, Ho, Er) compounds

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Infrared phonon modes and dielectric properties of La₂Zr₂O₇: Comparing thin film to bulk material

Infrared phonon modes and dielectric properties of La₂Zr₂O₇: Comparing thin film to bulk material