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Title: High-Pressure Study of Perovskites and Postperovskites in the (Mg,Fe)GeO 3 System

Abstract

The effect of incorporation of Fe 2+ on the perovskite (Pbnm) and postperovskite (Cmcm) structures was investigated in the (Mg,Fe)GeO 3 system at high pressures and temperatures using laser-heated diamond anvil cell and synchrotron X-ray diffraction. Samples with compositions of Mg# ≥ 48 were shown to transform to the perovskite (~30 GPa and ~1500 K) and postperovskite (>55 GPa, ~1600–1800 K) structures. Compositions with Mg# ≥ 78 formed single-phase perovskite and postperovskite, whereas those with Mg# < 78 showed evidence for partial decomposition. The incorporation of Fe into the perovskite structure causes a decrease in octahedral distortion as well as a modest decrease in bulk modulus (K 0) and a modest increase in zero-pressure volume (V 0). It also leads to a decrease in the perovskite-to-postperovskite phase transition pressure by ~9.5 GPa over compositions from Mg#78 to Mg#100.

Authors:
ORCiD logo [1];  [2];  [3];  [4];  [2]
  1. Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States; Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
  2. Department of Geosciences, Princeton University, Princeton, New Jersey 08544, United States
  3. Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
  4. GeoSoilEnviroCARS, University of Chicago, Argonne National Lab, Argonne, Illinois 60439, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCESNSF
OSTI Identifier:
1372253
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 56; Journal Issue: 14
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Stan, Camelia V., Dutta, Rajkrishna, Cava, Robert J., Prakapenka, Vitali B., and Duffy, Thomas S. High-Pressure Study of Perovskites and Postperovskites in the (Mg,Fe)GeO 3 System. United States: N. p., 2017. Web. doi:10.1021/acs.inorgchem.7b00774.
Stan, Camelia V., Dutta, Rajkrishna, Cava, Robert J., Prakapenka, Vitali B., & Duffy, Thomas S. High-Pressure Study of Perovskites and Postperovskites in the (Mg,Fe)GeO 3 System. United States. doi:10.1021/acs.inorgchem.7b00774.
Stan, Camelia V., Dutta, Rajkrishna, Cava, Robert J., Prakapenka, Vitali B., and Duffy, Thomas S. Thu . "High-Pressure Study of Perovskites and Postperovskites in the (Mg,Fe)GeO 3 System". United States. doi:10.1021/acs.inorgchem.7b00774.
@article{osti_1372253,
title = {High-Pressure Study of Perovskites and Postperovskites in the (Mg,Fe)GeO 3 System},
author = {Stan, Camelia V. and Dutta, Rajkrishna and Cava, Robert J. and Prakapenka, Vitali B. and Duffy, Thomas S.},
abstractNote = {The effect of incorporation of Fe2+ on the perovskite (Pbnm) and postperovskite (Cmcm) structures was investigated in the (Mg,Fe)GeO3 system at high pressures and temperatures using laser-heated diamond anvil cell and synchrotron X-ray diffraction. Samples with compositions of Mg# ≥ 48 were shown to transform to the perovskite (~30 GPa and ~1500 K) and postperovskite (>55 GPa, ~1600–1800 K) structures. Compositions with Mg# ≥ 78 formed single-phase perovskite and postperovskite, whereas those with Mg# < 78 showed evidence for partial decomposition. The incorporation of Fe into the perovskite structure causes a decrease in octahedral distortion as well as a modest decrease in bulk modulus (K0) and a modest increase in zero-pressure volume (V0). It also leads to a decrease in the perovskite-to-postperovskite phase transition pressure by ~9.5 GPa over compositions from Mg#78 to Mg#100.},
doi = {10.1021/acs.inorgchem.7b00774},
journal = {Inorganic Chemistry},
number = 14,
volume = 56,
place = {United States},
year = {Thu Jun 22 00:00:00 EDT 2017},
month = {Thu Jun 22 00:00:00 EDT 2017}
}
  • The 6H perovskites Ba{sub 3}MSb{sub 2}O{sub 9} (M = Mg, Ni, Zn) have been subjected to pressures of up to 5.5 GPa. No structural phase transitions were observed in Ba{sub 3}MgSb{sub 2}O{sub 9}. Ba{sub 3}NiSb{sub 2}O{sub 9} transformed from a phase containing Sb{sub 2}O{sub 9} dimers formed by face-sharing octahedra into a phase containing NiSbO{sub 9} dimers. This was confirmed by a combination of x-ray powder diffraction and EXAFS. Ba{sub 3}ZnSb{sub 2}O{sub 9} transformed into a cubic perovskite with a partial ordering of zinc and antimony over the octahedral sites.
  • We have studied the series of nominal composition BiCu{sub 3}(Mn{sub 4−x}Fe{sub x})O{sub 12} (x=0, 1.0, 2.0) where Mn is replaced by Fe cations in the ferrimagnetic perovskite BiCu{sub 3}Mn{sub 4}O{sub 12}. These compounds have been prepared from citrate precursors under moderate pressure conditions (3.5 GPa) and 1000 °C in the presence of KClO{sub 4} as oxidizing agent. All the samples have been studied by x-ray and neutron powder diffraction (NPD) at room temperature and 4 K. The crystal structure has been defined in a cubic Im3{sup ¯} (No. 204) space group with a 2a{sub 0}×2a{sub 0}×2a{sub 0} unit-cell. The doublingmore » of the unit-cell occurs due to the ordering of Bi{sup 3+} and Cu{sup 2+} cations over A sites of the AA′{sub 3}B{sub 4}O{sub 12} structure. The A-site accommodates 12-fold coordinated Bi{sup 3+} ions and, at the A′-site, Jahn–Teller Cu{sup 2+} ions form pseudo-square planar units aligned perpendicular to each other. Mn{sup 4+}/Fe{sup 3+} cations randomly occupy the centre of slightly distorted octahedra. These materials have also been characterized by magnetic and magnetotransport measurements. We found that all the samples are ferrimagnetic and show a progressive decrease of T{sub C} as the Fe content increases, since Fe ions disturb the ferromagnetic interactions within the B magnetic sublattice. In fact, the Curie temperature diminishes from T{sub C}=360 K (x=0) to T{sub C}=219 K (x=2). The magnetic structures, studied by low-temperature NPD data, correspond to an antiferromagnetic arrangement of spins at 8c and 6b sites; the ordered moments are in excellent agreement with those obtained from the saturation magnetization at 4 K. A significant magnetoresistant effect is determined for the x=1.0 oxide, with low-field values as high as 5% at 300 K and 1 T. Highlights: • BiCu{sub 3}(Mn{sub 4−x}Fe{sub x})O{sub 12} perovskites have been prepared under high pressure conditions. • They have been characterized by NPD, magnetic and magnetotransport measures. • The introduction of Fe leads to a transition from metallic to semiconducting. • Curie temperature decreases as the Fe content increases.« less
  • Perovskite phase formation and dielectric properties of the Pb(Fe[sub 2/3]W[sub 1/3])O[sub 3]-Pb(Mg[sub 1/3]Nb[sub 2/3])O[sub 3] system with substitution of Pb(Fe[sub 1/2]Nb[sub 1/2])O[sub 3] were studied. Ceramic powders were prepared by a B-site precursor method to enhance the perovskite formation yields. Lattice parameter changes were interpreted in terms of B-site cation stoichiometries and sizes. Weak-field low-frequency dielectric characteristics were investigated in order to examine the effect of composition modification on Curie temperatures and maximum dielectric constants.
  • The formation and properties of the post-perovskite (CaIrO{sub 3}-type) phase were studied in Fe-rich compositions along the pyrope-almandine ((Mg,Fe){sub 3}Al{sub 2}Si{sub 3}O{sub 12}) join. Natural and synthetic garnet starting materials with almandine fractions from 38 to 90 mol% were studied using synchrotron X-ray diffraction in the laser-heated diamond anvil cell. Single-phase post-perovskite could be successfully synthesized from garnet compositions at pressures above 148 GPa and temperatures higher than 1600 K. In some cases, evidence for a minor amount of Al{sub 2}O{sub 3} post-perovskite was observed for Alm38 and Alm54 compositions in the perovskite + post-perovskite two-phase region. Pressure-volume data formore » the post-perovskite phases collected during decompression show that incorporation of Fe leads to a systematic increase of unit cell volume broadly similar to the variation observed in the (Mg,Fe)SiO{sub 3} system. The presence of Al{sub 2}O{sub 3} increases the stability of perovskite relative to post-perovskite, requiring higher pressures (> 148 GPa) for synthesis of pure post-perovskites. Our data together with those of Tateno et al. (2005) also suggest that in the Al-rich system the presence of Fe has no strong effect on the pressure required to synthesize the pure post-perovskite phase, but the two-phase perovskite and post-perovskite region may be broad and its width dependent on Fe content. Our results suggest that any regions highly enriched in Al{sub 2}O{sub 3} may consist of either the perovskite phase or a mixture of perovskite and post-perovskite phases throughout the entire thickness of the D* region. The observed synthesis pressures (> 148 GPa) for a pure post-perovskite phase are beyond that at the Earth's core-mantle boundary ({approx} 135 GPa).« less