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Title: Raman and X-Ray Investigation of Pyrope Garnet (Mg{0.76}Fe{0.14}Ca{0.10}){2}A1{2}Si{3}O{12}

Abstract

The compressional behaviour of natural pyrope garnet is investigated by using angle-dispersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressure-induced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KT0 is 199 GPa, with its first pressure derivative K'T0 fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm-1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes (650-1000 cm-1) is larger than that of the low frequency (smaller than 650 cm-1). Based on these data, the mode Grueneisen parameters for pyrope are obtained.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
960166
Report Number(s):
BNL-83152-2009-JA
Journal ID: ISSN 0256-307X; CPLEEU; TRN: US1005913
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chinese Physics Letters; Journal Volume: 24; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 36 MATERIALS SCIENCE; BENDING; DIAMONDS; FREQUENCY RANGE; GARNETS; RAMAN SPECTRA; RAMAN SPECTROSCOPY; SYNCHROTRON RADIATION; X-RAY DIFFRACTION; national synchrotron light source

Citation Formats

Ma,Y., Chen, H., Li, X., Gao, L., Cui, Q., and Zou, G.. Raman and X-Ray Investigation of Pyrope Garnet (Mg{0.76}Fe{0.14}Ca{0.10}){2}A1{2}Si{3}O{12}. United States: N. p., 2007. Web.
Ma,Y., Chen, H., Li, X., Gao, L., Cui, Q., & Zou, G.. Raman and X-Ray Investigation of Pyrope Garnet (Mg{0.76}Fe{0.14}Ca{0.10}){2}A1{2}Si{3}O{12}. United States.
Ma,Y., Chen, H., Li, X., Gao, L., Cui, Q., and Zou, G.. Mon . "Raman and X-Ray Investigation of Pyrope Garnet (Mg{0.76}Fe{0.14}Ca{0.10}){2}A1{2}Si{3}O{12}". United States. doi:.
@article{osti_960166,
title = {Raman and X-Ray Investigation of Pyrope Garnet (Mg{0.76}Fe{0.14}Ca{0.10}){2}A1{2}Si{3}O{12}},
author = {Ma,Y. and Chen, H. and Li, X. and Gao, L. and Cui, Q. and Zou, G.},
abstractNote = {The compressional behaviour of natural pyrope garnet is investigated by using angle-dispersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressure-induced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KT0 is 199 GPa, with its first pressure derivative K'T0 fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm-1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes (650-1000 cm-1) is larger than that of the low frequency (smaller than 650 cm-1). Based on these data, the mode Grueneisen parameters for pyrope are obtained.},
doi = {},
journal = {Chinese Physics Letters},
number = 5,
volume = 24,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Garnets with compositions between majorite and pyrope, {ital M}{sub j38}, {ital M}{sub j48}, {ital M}{sub j75} and {ital M}{sub j79} were synthesized at high pressures and temperatures in a 2000-ton uniaxial split-sphere apparatus (USSA-2000) and investigated using high resolution synchrotron X-ray powder diffraction and transmission electron microscopy. The results from both techniques are consistent with the tetragonal field for these garnets extending to a majorite composition just below {ital M}{sub j75}. The cubic-tetragonal structural phase transition in garnet along the majorite-pyrope join is sensitive to both composition and temperature and is expected to result in anomalous behavior in elastic shearmore » moduli. This phase transition may occur in the transition zone of the earth{close_quote}s mantle and will have important effects on the elastic and rheological properties of this region where these garnets are stable phases. {copyright} American Geophysical Union 1996« less
  • The heat capacity of Mg{sub 3}Al{sub 2}Si{sub 3}O{sub 12} glass has been measured from 10 to 1000 K by adiabatic and differential scanning calorimetry. The heat capacity of crystalline pyrope has been determined from drop-calorimetry measurements between 820 and 1300 K. From these and previously published results a consistent set of thermodynamic data is presented for pyrope and Mg{sub 3}Al{sub 2}Si{sub 3}O{sub 12} glass and liquid for the interval 0-2000 K. The enthalpy of fusion at 1570 {plus minus} 30 K, the metastable congruent 1-bar melting point, is 241 {plus minus} 12 kJ/mol.
  • High-order Stokes and anti-Stokes generation in the visible and near-infrared in cubic laser crystal hosts Gd{sub 3}Ga{sub 5}O{sub 12}, Gd{sub 3}Sc{sub 2}Ga{sub 3}O{sub 12}, and Ca{sub 3}(Nb,Ga){sub 2}Ga{sub 3}O{sub 12} was observed for the first time. All scattering-laser components were identified and attributed to the SRS-active vibration modes of these garnet crystals. (letters to the editor)
  • The heat capacity of synthetic andradite garnet (Ca/sub 3/Fe/sub 2/Si/sub 3/O/sub 12/) was measured between 9.6 and 365.5 K by cryogenic adiabatic calorimetry and from 340 to 990 K by differential scanning calorimetry. At 298.15 K C/sub p,m//sup 0/ and S/sub m//sup 0/ are 351.9 +- 0.7 and 316.4 +- 2.0 J(mol x K), respectively. Andradite has a lambda-peak in C/sub p,m//sup 0/ with a maximum at 11.7 +- 0.2 K which is presumably associated with the antiferromagnetic ordering of the magnetic moments of the Fe/sup 3 +/ ions. The Gibbs free energy of formation, ..delta../sub f/G/sub m//sup 0/ (298.15more » K) of andradite is -5414.8 +- 5.5 kJmol, and was obtained by combining our entropy and heat capacity data with the known breakdown of andradite to pseudowollastonite and hematite at approx. 1410 to 1438 K. From a reexamination of the calcite + quartz = wollastonite equilibrium data we obtained ..delta../sub f/H/sub m//sup 0/ (298.15 K) = -1634.5 +- 1.8 kJmol for wollastonite. The authors have also used their thermochemical data for andradite to estimate the Gibbs free energy of formation of hedenbergite (CaFeSi/sub 2/O/sub 6/) for which we obtained ..delta../sub f/G/sub m//sup 0/ (298.15 K) = -2674.3 +- 5.8 kJmol.« less