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Title: Crystal growth and structure of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) using molten KF

Abstract

Single crystals of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) have been synthesized using molten KF at 1373K. The pyrochlore compounds crystallize in a cubic space group Fd3-barm (No. 227, origin choice 2), with Z=8. At room temperature, the lattice parameters are a=10.3940(4)A, V=1122.92(7)A{sup 3} and a=10.274(3)A, V=1084.5(6)A{sup 3} for Pr{sub 2}Ir{sub 2}O{sub 7} and Eu{sub 2}Ir{sub 2}O{sub 7}, respectively. In this paper, we report the crystal growth of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) and their structure determinations from single crystal X-ray diffraction experiments at temperatures of 110, 115, and 298K.

Authors:
 [1];  [1];  [2];  [3];  [2];  [2];  [4];  [5]
  1. Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803 (United States)
  2. Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)
  3. (ISSP), University of Tokyo, Kashiwa 277-8581 (Japan)
  4. (Japan)
  5. Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803 (United States). E-mail: jchan@lsu.edu
Publication Date:
OSTI Identifier:
21000638
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 42; Journal Issue: 5; Other Information: DOI: 10.1016/j.materresbull.2006.08.011; PII: S0025-5408(06)00343-6; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL GROWTH; CUBIC LATTICES; LATTICE PARAMETERS; MONOCRYSTALS; OXIDES; POTASSIUM FLUORIDES; PYROCHLORE; SPACE GROUPS; X-RAY DIFFRACTION

Citation Formats

Millican, Jasmine N., Macaluso, Robin T., Nakatsuji, Satoru, Institute for Solid State Physics, Machida, Yo, Maeno, Yoshiteru, International Innovation Center, Kyoto University, Kyoto 606-8501, and Chan, Julia Y. Crystal growth and structure of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) using molten KF. United States: N. p., 2007. Web. doi:10.1016/j.materresbull.2006.08.011.
Millican, Jasmine N., Macaluso, Robin T., Nakatsuji, Satoru, Institute for Solid State Physics, Machida, Yo, Maeno, Yoshiteru, International Innovation Center, Kyoto University, Kyoto 606-8501, & Chan, Julia Y. Crystal growth and structure of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) using molten KF. United States. doi:10.1016/j.materresbull.2006.08.011.
Millican, Jasmine N., Macaluso, Robin T., Nakatsuji, Satoru, Institute for Solid State Physics, Machida, Yo, Maeno, Yoshiteru, International Innovation Center, Kyoto University, Kyoto 606-8501, and Chan, Julia Y. Thu . "Crystal growth and structure of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) using molten KF". United States. doi:10.1016/j.materresbull.2006.08.011.
@article{osti_21000638,
title = {Crystal growth and structure of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) using molten KF},
author = {Millican, Jasmine N. and Macaluso, Robin T. and Nakatsuji, Satoru and Institute for Solid State Physics and Machida, Yo and Maeno, Yoshiteru and International Innovation Center, Kyoto University, Kyoto 606-8501 and Chan, Julia Y.},
abstractNote = {Single crystals of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) have been synthesized using molten KF at 1373K. The pyrochlore compounds crystallize in a cubic space group Fd3-barm (No. 227, origin choice 2), with Z=8. At room temperature, the lattice parameters are a=10.3940(4)A, V=1122.92(7)A{sup 3} and a=10.274(3)A, V=1084.5(6)A{sup 3} for Pr{sub 2}Ir{sub 2}O{sub 7} and Eu{sub 2}Ir{sub 2}O{sub 7}, respectively. In this paper, we report the crystal growth of R{sub 2}Ir{sub 2}O{sub 7} (R=Pr, Eu) and their structure determinations from single crystal X-ray diffraction experiments at temperatures of 110, 115, and 298K.},
doi = {10.1016/j.materresbull.2006.08.011},
journal = {Materials Research Bulletin},
number = 5,
volume = 42,
place = {United States},
year = {Thu May 03 00:00:00 EDT 2007},
month = {Thu May 03 00:00:00 EDT 2007}
}
  • Although R{sub 2}O{sub 3}:MoO{sub 3}=1:6 (R=rare earth) compounds are known in the R{sub 2}O{sub 3}-MoO{sub 3} phase diagrams since a long time, no structural characterization has been achieved because a conventional solid-state reaction yields powder samples. We obtained single crystals of R{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O (R=Pr, Nd, Sm, and Eu) by thermal decomposition of [R{sub 2}(H{sub 2}O){sub 12}Mo{sub 8}O{sub 27}].nH{sub 2}O at around 685-715{sup o}C for 2h, and determined their crystal structures. The simulated XRD patterns of R{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O were consistent with those of previously reported R{sub 2}O{sub 3}:MoO{sub 3}=1:6 compounds. All R{sub 2}Mo{sub 6}O{sub 21}.H{submore » 2}O compounds crystallize isostructurally in tetragonal, P4/ncc (No. 130), a=8.9962(5), 8.9689(6), 8.9207(4), and 8.875(2)A; c=26.521(2), 26.519(2), 26.304(2), and 26.15(1)A; Z=4; R{sub 1}=0.026, 0.024, 0.024, and 0.021, for R=Pr, Nd, Sm, and Eu, respectively. The crystal structure of R{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O consists of two [Mo{sub 2}O{sub 7}]{sup 2-}-containing layers (A and B layers) and two interstitial R(1){sup 3+} and R(2){sup 3+} cations. Each [Mo{sub 2}O{sub 7}]{sup 2-} group is composed of two corner-sharing [MoO{sub 4}] tetrahedra. The [Mo{sub 2}O{sub 7}]{sup 2-} in the B layer exhibits a disorder to form a pseudo-[Mo{sub 4}O{sub 9}] group, in which four Mo and four O sites are half occupied. R(1){sup 3+} achieves 8-fold coordination by O{sup 2-} to form a [R(1)O{sub 8}] square antiprism, while R(2){sup 3+} achieves 9-fold coordination by O{sup 2-} and H{sub 2}O to form a [R(2)(H{sub 2}O)O{sub 8}] monocapped square antiprism. The disorder of the [Mo{sub 2}O{sub 7}]{sup 2-} group in the B layer induces a large displacement of the O atoms in another [Mo{sub 2}O{sub 7}]{sup 2-} group (in the A layer) and in the [R(1)O{sub 8}] and [R(2)(H{sub 2}O)O{sub 8}] polyhedra. A remarkable broadening of the photoluminescence spectrum of Eu{sub 2}Mo{sub 6}O{sub 21}.H{sub 2}O supported the large displacement of O ligands coordinating Eu(1) and Eu(2)« less
  • We conducted a detailed study of the structure and magnetic properties of ([ital R][sub 1[minus][ital x]]Pr[sub [ital x]])Ba[sub 2]Cu[sub 3]O[sub 7] sintered samples, where [ital R]=Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, Sm, and Nd for [ital x]=0.5--1.0. We found that the temperature dependence of the dc susceptibility follows the Curie-Weiss law in the temperature range 20--300 K and the paramagnetism of the Pr and [ital R] sublattices exist independently of one another. The antiferromagnetic ordering temperature [ital T][sub [ital N]] of Pr ions decreases monotonically with increasing [ital R] concentration (1[minus][ital x]). At a given [ital x],more » [ital T][sub [ital N]] is [ital R]-ion-size dependent. The slope in the [ital T][sub [ital N]] vs [ital x] curve is steeper for ions with smaller ionic radii. The observed results are interpreted in terms of the hybridization between the local states of the Pr ion and the valence-band states of the CuO[sub 2] planes.« less
  • We observed that the superconducting critical temperature {ital T}{sub {ital c}}({ital x}) of the oxides (R{sub 1{minus}{ital x}}Pr{sub {ital x}})Ba{sub 2}Cu{sub 3}O{sub 7{minus}{ital y}} (R=Er, Y, Dy, Gd, Eu) decreases monotonically with increasing Pr concentration {ital x}. Using the reduced parameters {ital T}{sub {ital c}}/{ital T}{sub {ital c}}(0) and {ital x}/{ital x}{sub {ital cr}} all the experimental data for five studied systems fall onto the theoretical universal curve of Abrikosov and Gor'kov over the reduced Pr concentration regime, {ital x}/{ital x}{sub {ital cr}}{lt}0.6, where {ital x}{sub {ital cr}} is the critical concentration of Pr for the complete suppression of superconductivitymore » and {ital T}{sub {ital c}}(0) is the {ital T}{sub {ital c}} for undoped material. The consistency of these results suggests a pair-breaking mechanism which plays a role in depressing superconductivity in these high {ital T}{sub {ital c}} oxides.« less
  • We report detailed studies of the normal-state resistivity and the Hall-effect in bulk {ital R}{sub 0.8}Pr{sub 0.2}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{ital y}} samples ({ital R}=Yb, Er, Dy, Gd, Eu, and Nd). We find a linear temperature dependence of the normal-state resistivity {rho}{sub {ital u}} and the Hall number {ital n}{sub {ital H}} above {ital T}{sub {ital c}} in these systems. At a constant temperature both {rho}{sub {ital n}} and {ital n}{sub {ital H}} are linearly dependent on the ion-size of the rare earth, viz., the larger {ital R}{sup 3+} ionic radius, the larger {rho}{sub {ital n}}, but the lower {ital n}{submore » {ital H}}. The cotangent of the Hall angle follows a universal {ital T}{sup 2} dependence, i.e., cot{theta}{sub {ital H}}={alpha}{ital T}{sup 2}+{ital C}. Both the slope {alpha} and the quantity {ital C} is insensitive to the {ital R} ion and remains almost constant. On the basis of our data we propose a {ital T}{sub {ital c}}-{ital n}{sub {ital H}} diagram which manifests an {open_quote}{open_quote}underdoping{close_quote}{close_quote} behavior of {ital R}{sub 0.8}Pr{sub 0.2}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{ital y}} systems. We suggest that the strong hybridization between the 4{ital f} states of the Pr ion and the conduction-band states in CuO{sub 2} planes, leading to hole localization and pair breaking, are the mechanism for the suppression of superconductivity in {ital R}{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{ital y}} systems. {copyright} {ital 1996 The American Physical Society.}« less
  • The crystal structures of the new ternary compounds Sm{sub 4}Ir{sub 13}Ge{sub 9} and LaIr{sub 3}Ge{sub 2} were determined and refined on the basis of single-crystal X-ray diffraction data. They belong to the Ho{sub 4}Ir{sub 13}Ge{sub 9} (oP52, Pmmn) and CeCo{sub 3}B{sub 2} (hP5, P6/mmm) structure types, respectively. The formation of isotypic compounds R{sub 4}Ir{sub 13}Ge{sub 9} with R=La, Ce, Pr, Nd, and RIr{sub 3}Ge{sub 2} with R=Ce, Pr, Nd, was established by powder X-ray diffraction. The RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd) compounds exist only in as-cast samples and decompose during annealing at 800 Degree-Sign C with the formationmore » of R{sub 4}Ir{sub 13}Ge{sub 9}. The structure of Sm{sub 4}Ir{sub 13}Ge{sub 9} contains intersecting, slightly puckered nets of Ir atoms (4{sup 4})(4{sup 3}.6){sub 2}(4.6{sup 2}){sub 2} and (4{sup 4}){sub 2}(4{sup 3}.6){sub 4}(4.6{sup 2}){sub 2} that are perpendicular to [0 1 1] as well as to [0 -1 1] and [0 0 1]. The Ir atoms are surrounded by Ge atoms that form tetrahedra or square pyramids (where the layers intersect). The Sm and additional Ir atoms (in trigonal-planar coordination) are situated in channels along [1 0 0] (short translation vector). In the structure of LaIr{sub 3}Ge{sub 2} the Ir atoms form planar Kagome nets (3.6.3.6) perpendicular to [0 0 1]. These nets alternate along the short translation vector with layers of La and Ge atoms. - Graphical abstract: The crystal structures contain the nets of Ir atoms as main structural motif: R{sub 4}Ir{sub 13}Ge{sub 9} contains intersecting slightly puckered nets of Ir atoms, whereas in the structure of RIr{sub 3}Ge{sub 2} the Ir atoms form planar Kagome nets. Highlights: Black-Right-Pointing-Pointer The Ir-rich ternary germanides R{sub 4}Ir{sub 13}Ge{sub 9} (R=La, Ce, Pr, Nd, Sm) and RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd) have been synthesized. Black-Right-Pointing-Pointer The RIr{sub 3}Ge{sub 2} compounds exist only in as-cast samples and decompose during annealing at 800 Degree-Sign C with the formation of R{sub 4}Ir{sub 13}Ge{sub 9}. Black-Right-Pointing-Pointer The structure of R{sub 4}Ir{sub 13}Ge{sub 9} contains intersecting slightly puckered nets of Ir atoms. Black-Right-Pointing-Pointer In the structure of RIr{sub 3}Ge{sub 2} the Ir atoms form planar Kagome nets.« less