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Title: Crack resistance and atomic structure of Li{sub 2}B{sub 4}O{sub 7} single crystals

Abstract

The nature of destruction of single crystals of lithium tetraborate Li{sub 2}B{sub 4}O{sub 7} under the action of a concentrated load is investigated. It is established that planes of easy crack propagation in Li{sub 2}B{sub 4}O{sub 7} single crystals are the (100), (010), (001), and {l_brace}111{r_brace} planes. It is found that crack propagation occurs in each case along the atomic layers that are linked by bridge oxygen atoms between main structural units (B{sub 4}O{sub 9}) and, therefore, are most weakly bound.

Authors:
; ;  [1]
  1. National Academy of Sciences of Ukraine, Institute for Single Crystals (Ukraine)
Publication Date:
OSTI Identifier:
21091494
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 51; Journal Issue: 2; Other Information: DOI: 10.1134/S1063774506020167; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BORATES; CRACK PROPAGATION; CRACKS; LITHIUM COMPOUNDS; MONOCRYSTALS

Citation Formats

Dolzhenkova, E. F., E-mail: dol@isc.kharkov.ua, Baumer, V. N., and Tolmachev, A. V. Crack resistance and atomic structure of Li{sub 2}B{sub 4}O{sub 7} single crystals. United States: N. p., 2006. Web. doi:10.1134/S1063774506020167.
Dolzhenkova, E. F., E-mail: dol@isc.kharkov.ua, Baumer, V. N., & Tolmachev, A. V. Crack resistance and atomic structure of Li{sub 2}B{sub 4}O{sub 7} single crystals. United States. doi:10.1134/S1063774506020167.
Dolzhenkova, E. F., E-mail: dol@isc.kharkov.ua, Baumer, V. N., and Tolmachev, A. V. Wed . "Crack resistance and atomic structure of Li{sub 2}B{sub 4}O{sub 7} single crystals". United States. doi:10.1134/S1063774506020167.
@article{osti_21091494,
title = {Crack resistance and atomic structure of Li{sub 2}B{sub 4}O{sub 7} single crystals},
author = {Dolzhenkova, E. F., E-mail: dol@isc.kharkov.ua and Baumer, V. N. and Tolmachev, A. V.},
abstractNote = {The nature of destruction of single crystals of lithium tetraborate Li{sub 2}B{sub 4}O{sub 7} under the action of a concentrated load is investigated. It is established that planes of easy crack propagation in Li{sub 2}B{sub 4}O{sub 7} single crystals are the (100), (010), (001), and {l_brace}111{r_brace} planes. It is found that crack propagation occurs in each case along the atomic layers that are linked by bridge oxygen atoms between main structural units (B{sub 4}O{sub 9}) and, therefore, are most weakly bound.},
doi = {10.1134/S1063774506020167},
journal = {Crystallography Reports},
number = 2,
volume = 51,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • Single crystals of the new compounds Li{sub 6}[(UO{sub 2}){sub 12}(PO{sub 4}){sub 8}(P{sub 4}O{sub 13})] (1), Li{sub 5}[(UO{sub 2}){sub 13}(AsO{sub 4}){sub 9}(As{sub 2}O{sub 7})] (2), Li[(UO{sub 2}){sub 4}(AsO{sub 4}){sub 3}] (3) and Li{sub 3}[(UO{sub 2}){sub 7}(AsO{sub 4}){sub 5}O)] (4) have been prepared using high-temperature solid state reactions. The crystal structures have been solved by direct methods: 1-monoclinic, C2/m, a=26.963(3) A, b=7.063(1) A, c=19.639(1) A, beta=126.890(4){sup o}, V=2991.2(6) A{sup 3}, Z=2, R{sub 1}=0.0357 for 3248 unique reflections with |F{sub 0}|>=4sigma{sub F}; 2-triclinic, P1-bar, a=7.1410(8) A, b=13.959(1) A, c=31.925(1) A, alpha=82.850(2){sup o}, beta=88.691(2){sup o}, gamma=79.774(3){sup o}, V=3107.4(4) A{sup 3}, Z=2, R{sub 1}=0.0722 formore » 9161 unique reflections with |F{sub 0}|>=4sigma{sub F}; 3-tetragonal, I4{sub 1}/amd, a=7.160(3) A, c=33.775(9) A, V=1732(1) A{sup 3}, Z=4, R{sub 1}=0.0356 for 318 unique reflections with |F{sub 0}|>=4sigma{sub F}; 4-tetragonal, P4-bar, a=7.2160(5) A, c=14.6540(7) A, V=763.04(8) A{sup 3}, Z=1, R{sub 1}=0.0423 for 1600 unique reflections with |F{sub 0}|>=4sigma{sub F}. Structures of all the phases under consideration are based on complex 3D frameworks consisting of different types of uranium polyhedra (UO{sub 6} and UO{sub 7}) and different types of tetrahedral TO{sub 4} anions (T=P or As): PO{sub 4} and P{sub 4}O{sub 13} in 1, AsO{sub 4} and As{sub 2}O{sub 7} in 2, and single AsO{sub 4} tetrahedra in 3 and 4. In the structures of 1 and 2, UO{sub 7} pentagonal bipyramids share edges to form (UO{sub 5}){sub i}nfinity chains extended along the b axis in 1 and along the a axis in 2. The chains are linked via single TO{sub 4} tetrahedra into tubular units with external diameters of 11 A in 1 and 11.5 A in 2, and internal diameters of 4.1 A in 1 and 4.5 A in 2. The channels accommodate Li{sup +} cations. The tubular units are linked into 3D frameworks by intertubular complexes. Structures of 3 and 4 are based on 3D frameworks composed on layers united by (UO{sub 5}){sub i}nfinity infinite chains. Cation-cation interactions are observed in 2, 3, and 4. In 2, the structure contains a trimeric unit with composition [O=U(1)=O]-U(13)-[O=U(2)=O]. In the structures of 3 and 4, T-shaped dimers are observed. In all the structures, Li{sup +} cations are located in different types of cages and channels and compensate negative charges of anionic 3D frameworks. - Graphical abstract: The crystal structures of Li{sub 5}[(UO{sub 2}){sub 13}(AsO{sub 4}){sub 9}(As{sub 2}O{sub 7})] separated into tubular units and intertubular complexes.« less
  • Four new Li uranyl phosphates and arsenates have been prepared by high-temperature solid-state reactions: {alpha}-Li[(UO{sub 2})(PO{sub 4})] (1), {alpha}-Li[(UO{sub 2})(AsO{sub 4})] (2), {beta}-Li[(UO{sub 2})(AsO{sub 4})] (3) and Li{sub 2}[(UO{sub 2}){sub 3}(P{sub 2}O{sub 7}){sub 2}] (4). The structures of the compounds have been solved by direct methods: 1-triclinic, P1-bar, a=5.0271(1) A, b=9.8799(2) A, c=10.8920(2) A, {alpha}=108.282(9){sup o}, {beta}=102.993(8){sup o}, {gamma}=104.13(1){sup o}, V=470.69(2) A{sup 3}, Z=4, R{sub 1}=0.0415 for 2786 unique reflections with |F{sub 0}|{>=}4{sigma}{sub F}; 2-triclinic, P1-bar, a=5.129(2) A, b=10.105(3) A, c=11.080(3) A, {alpha}=107.70(2){sup o}, {beta}=102.53(3){sup o}, {gamma}=104.74(3){sup o}, V=501.4(3) A{sup 3}, Z=4, R{sub 1}=0.055 for 1431 unique reflections with |F{submore » 0}|{>=}4{sigma}{sub F}; 3-triclinic, P1-bar, a=5.051(1) A, b=5.303(1) A, c=10.101(1) A, {alpha}=90.31(1){sup o}, {beta}=97.49(1){sup o}, {gamma}=105.08(1){sup o}, V=258.80(8) A{sup 3}, Z=2, R{sub 1}=0.0339 for 2055 unique reflections with |F{sub 0}|{>=}4{sigma}{sub F}; 4-triclinic, P1-bar, a=5.312(1) A, b=6.696(1) A, c=12.542(1) A, {alpha}=94.532(9){sup o}, {beta}=99.059(8){sup o}, {gamma}=110.189(7){sup o}, V=409.17(10) A{sup 3}, Z=2, R{sub 1}=0.0565 for 1355 unique reflections with |F{sub 0}|{>=}4{sigma}{sub F}. The structures of all four compounds are based upon 3-D frameworks of U and T polyhedra (T=P, As). Phases 1 and 2 are isostructural and consist of U{sub 2}O{sub 12} dimers and UO{sub 6} square bipyramids linked by single TO{sub 4} tetrahedra. The structure of 3 consists of 3-D framework of corner-sharing UO{sub 6} bipyramids and AsO{sub 4} tetrahedra. In the structure of 4, the framework is composed of U{sub 2}O{sub 12} dimers, UO{sub 6} bipyramids and P{sub 2}O{sub 7} dimers. In all the compounds, Li{sup +} cations reside in framework cavities. The topologies of the 3-D frameworks can be described as derivatives of the PtS (cooperite) network. - Graphical abstract: Polyhedral and topological presentation of Li{sub 2}[(UO{sub 2}){sub 3}(P{sub 2}O{sub 7}){sub 2}] crystal structure.« less
  • The reaction of Re{sub 2}O{sub 7} with XeF{sub 6} in anhydrous HF provides a convenient route to high-purity ReO{sub 2}F{sub 3}. The fluoride acceptor and Lewis base properties of ReO{sub 2}F{sub 3} have been investigated leading to the formation of [M][ReO{sub 2}F{sub 4}] [M = Li, Na, Cs, N(CH{sub 3}){sub 4}], [K][Re{sub 2}O{sub 4}F{sub 7}], [K][Re{sub 2}O{sub 4}F{sub 7}]{center_dot}2ReO{sub 2}F{sub 3}, [Cs][Re{sub 3}O{sub 6}F{sub 10}], and ReO{sub 2}F{sub 3}(CH{sub 3}CN). The ReO{sub 2}F{sub 4}{sup {minus}}, Re{sub 2}O{sub 4}F{sub 7}{sup {minus}}, and Re{sub 3}O{sub 6}F{sub 10{sup {minus}} anions and the ReO{sub 2}F{sub 3}(CH{sub 3}CN) adduct have been characterized in the solidmore » state by Raman spectroscopy, and the structures [Li][ReO{sub 2}F{sub 4}], [K][Re{sub 2}O{sub 4}F{sub 7}], [K][Re{sub 2}O{sub 4}F{sub 7}]{center_dot}2ReO{sub 2}F{approximately}3}, [Cs][Re{sub 3}O{sub 6}F{sub 10}], and ReO{sub 3}F(CH{sub 3}CN){sub 2}{center_dot}CH{sub 3}CN have been determined by X-ray crystallography. The structure of ReO{sub 2}F{sub 4}{sup {minus}} consists of a cis-dioxo arrangement of Re-O double bonds in which the Re-F bonds trans to the oxygen atoms are significantly lengthened as a result of the trans influence of the oxygens. The Re{sub 2}O{sub 4}F{sub 7}{sup {minus}} and Re{sub 3}O{sub 6}F{sub 10}{sup {minus}} anions and polymeric ReO{sub 2}F{sub 3} are open chains containing fluorine-bridged ReO{sub 2}F{sub 4} units in which each pair of Re-O bonds are cis to each other and the fluorine bridges are trans to oxygens. The trans influence of the oxygens is manifested by elongated terminal Re-F bonds trans to Re-O bonds as in ReO{sub 2}F{sub 4}{sup {minus}} and by the occurrence of both fluorine bridges trans to Re-O bonds. Fluorine-19 NMR spectra show that ReO{sub 2}F{sub 4}{sup {minus}}, Re{sub 2}O{sub 4}F{sub 7}{sup {minus}}, and ReO{sub 2}F{sub 3}(CH{sub 3}CN) have cis-dioxo arrangements in CH{sub 3}CN solution. Density functional theory calculations at the local and nonlocal levels confirm that the cis-dioxo isomers of ReO{sub 2}F{sub 4}{sup {minus}} and ReO{sub 2}F{sub 3}(CH{sub 3}CN), where CH{sub 3}CN is bonded trans to an oxygen, are the energy-minimized structures. The adduct ReO{sub 3}F(CH{sub 3}CN){sub 2}{center_dot}CH{sub 3}CN was obtained by hydrolysis of ReO{sub 2}F{sub 3}(CH{sub 3}CN), and was shown by X-ray crystallography to have a facial arrangement of oxygen atoms on rhenium.« less
  • Atomic force microscopy has been applied to study the surfaces of Y[sub 2]Ba[sub 4]Cu[sub 7]O[sub 15] (247) and YBa[sub 2]Cu[sub 4]O[sub 8] (124) high-temperature superconductor single crystals at ambient temperature and pressure. In contrast to very thin ([lt]10 [mu]m) crystal platelets, which exhibit by scanning tunneling microscopy clean terraces with steps of the height of one or multiple unit cells, thicker crystals show surfaces partially covered by a contamination layer with a highly curved boundary line originating from BaCuO[sub 2]/CuO flux used to grow 124 and 247 single crystals under high oxygen pressure. The evaluation of the length of suchmore » flux boundaries by the box counting method reveals that they are fractal with a fractal dimension of about 1.4. Close to crystal steps, higher fractal dimensions are observed provided the terrace width is sufficiently large. The fact that the residual flux is always found on the lower terrace level of a crystal step allows discussion of a possible mechanism of flux migration on the crystal surface.« less
  • The possibility of determining the optimal compositions and temperatures of supersaturated solutions for enhanced growth of single crystals of congruently and incongruently dissolving solid phases from the solubility diagrams of ternary systems is shown, and this approach is justified. The NiSO{sub 4}-H{sub 2}SO{sub 4}-H{sub 2}O, Me{sub 2}SO{sub 4}-NiSO{sub 4}-H{sub 2}O, and Me{sub 2}O-P{sub 2}O{sub 5}-H{sub 2}O(D{sub 2}O) systems have been used to determine the optimal compositions and temperatures of supersaturated solutions for growth of {alpha}-NiSO{sub 4} . 6H{sub 2}O, Me{sub 2}Ni(SO{sub 4}){sub 2} . 6H{sub 2}O, MeH{sub 2}PO{sub 4} [Me = Li, Na, K, Rb, Cs, NH{sub 4}], and Kmore » (H{sub x} D{sub 1-x}){sub 2}PO{sub 4} (D is deuterium) single crystals.« less