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Title: The Pr{sub 2}Se{sub 3}-PrSe{sub 2} system: Studies of the phase relationships and the modulated crystal structure of PrSe{sub 1.85}

Abstract

Thermochemical investigations have been carried out to elucidate the phase relationships in the system Pr{sub 2}Se{sub 3}-PrSe{sub 2} and to construct the p{sub Se}-T-x diagram. The result of the tensimetric and thermogravimetric studies showed the thermal decomposition of PrSe{sub 2} to be a step-wise process due to the formation of a sequence of discrete intermediate phases with the compositions PrSe{sub 1.9}, PrSe{sub 1.85}, PrSe{sub 1.8}, and Pr{sub 2}Se{sub 3}. PrSe{sub 1.85} and PrSe{sub 1.8} have been previously considered as selenium-deficient non-stoichiometric phases. Conclusions derived from the thermodynamic study were verified by X-ray diffraction and electron microscopy studies on single crystals of PrSe{sub 1.85} which were obtained from reactions of praseodymium and selenium in stoichiometric amounts in a KCl flux at 1070K. A two-dimensional modulation could be observed for PrSe{sub 1.85} in X-ray and high-resolution transmission electron microscopy. The structure of PrSe{sub 1.85} was solved and refined in superspace group P4/n({alpha}{beta}12)({beta}-{alpha}12)00 with lattice parameters of a=4.137(1)A, c=8.398(2)A of the basic unit cell and {alpha}={beta}=0.293(1). The origin of the modulation can be attributed to a site occupancy wave and a charge density wave in its planar selenium layer. The experimentally determined magnetic moments indicate Pr{sup 3+} for the polyselenides PrSe{sub 2}, PrSe{submore » 1.9} and PrSe{sub 1.85}.« less

Authors:
 [1];  [2];  [2];  [3];  [4];  [4]
  1. Inorganic Chemistry, Dresden University of Technology, Helmholtzstr. 10, 01069 Dresden (Germany), E-mail: thomas.doert@chemie.tu-dresden.de
  2. Inorganic Chemistry, Dresden University of Technology, Helmholtzstr. 10, 01069 Dresden (Germany)
  3. A. V. Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Ave. 3, Novosibirsk, 630090 (Russian Federation)
  4. Max Planck Institute for Chemical Physics of Solids, Noethnitzer Str. 40, 01187 Dresden (Germany)
Publication Date:
OSTI Identifier:
21015676
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 2; Other Information: DOI: 10.1016/j.jssc.2006.10.030; PII: S0022-4596(06)00581-0; 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:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CHARGE DENSITY; DIAGRAMS; LATTICE PARAMETERS; LAYERS; MAGNETIC MOMENTS; MONOCRYSTALS; PHASE STUDIES; POTASSIUM CHLORIDES; PRASEODYMIUM IONS; PRASEODYMIUM SELENIDES; PYROLYSIS; TEMPERATURE RANGE 1000-4000 K; TETRAGONAL LATTICES; THERMAL GRAVIMETRIC ANALYSIS; TRANSMISSION ELECTRON MICROSCOPY; X RADIATION; X-RAY DIFFRACTION

Citation Formats

Doert, Thomas, Graf, Christian, Schmidt, Peer, Vasilieva, Inga G., Simon, Paul, and Carrillo-Cabrera, Wilder. The Pr{sub 2}Se{sub 3}-PrSe{sub 2} system: Studies of the phase relationships and the modulated crystal structure of PrSe{sub 1.85}. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2006.10.030.
Doert, Thomas, Graf, Christian, Schmidt, Peer, Vasilieva, Inga G., Simon, Paul, & Carrillo-Cabrera, Wilder. The Pr{sub 2}Se{sub 3}-PrSe{sub 2} system: Studies of the phase relationships and the modulated crystal structure of PrSe{sub 1.85}. United States. doi:10.1016/j.jssc.2006.10.030.
Doert, Thomas, Graf, Christian, Schmidt, Peer, Vasilieva, Inga G., Simon, Paul, and Carrillo-Cabrera, Wilder. Thu . "The Pr{sub 2}Se{sub 3}-PrSe{sub 2} system: Studies of the phase relationships and the modulated crystal structure of PrSe{sub 1.85}". United States. doi:10.1016/j.jssc.2006.10.030.
@article{osti_21015676,
title = {The Pr{sub 2}Se{sub 3}-PrSe{sub 2} system: Studies of the phase relationships and the modulated crystal structure of PrSe{sub 1.85}},
author = {Doert, Thomas and Graf, Christian and Schmidt, Peer and Vasilieva, Inga G. and Simon, Paul and Carrillo-Cabrera, Wilder},
abstractNote = {Thermochemical investigations have been carried out to elucidate the phase relationships in the system Pr{sub 2}Se{sub 3}-PrSe{sub 2} and to construct the p{sub Se}-T-x diagram. The result of the tensimetric and thermogravimetric studies showed the thermal decomposition of PrSe{sub 2} to be a step-wise process due to the formation of a sequence of discrete intermediate phases with the compositions PrSe{sub 1.9}, PrSe{sub 1.85}, PrSe{sub 1.8}, and Pr{sub 2}Se{sub 3}. PrSe{sub 1.85} and PrSe{sub 1.8} have been previously considered as selenium-deficient non-stoichiometric phases. Conclusions derived from the thermodynamic study were verified by X-ray diffraction and electron microscopy studies on single crystals of PrSe{sub 1.85} which were obtained from reactions of praseodymium and selenium in stoichiometric amounts in a KCl flux at 1070K. A two-dimensional modulation could be observed for PrSe{sub 1.85} in X-ray and high-resolution transmission electron microscopy. The structure of PrSe{sub 1.85} was solved and refined in superspace group P4/n({alpha}{beta}12)({beta}-{alpha}12)00 with lattice parameters of a=4.137(1)A, c=8.398(2)A of the basic unit cell and {alpha}={beta}=0.293(1). The origin of the modulation can be attributed to a site occupancy wave and a charge density wave in its planar selenium layer. The experimentally determined magnetic moments indicate Pr{sup 3+} for the polyselenides PrSe{sub 2}, PrSe{sub 1.9} and PrSe{sub 1.85}.},
doi = {10.1016/j.jssc.2006.10.030},
journal = {Journal of Solid State Chemistry},
number = 2,
volume = 180,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • The chemistry and structural chemistry versus temperature in the system UO/sub 3/-SeO/sub 2/-H/sub 2/O were determined. A proposal has been presented for the structural transformations of various selenites, i.e., UO/sub 2/Se/sub 2/O/sub 5/ x 2H/sub 2/O, UO/sub 2/Se/sub 2/O/sub 5/, UO/sub 2/SeO/sub 3/, and the U/sub 3/O/sub 8/ uranium oxide final product in its ..beta.. form. The unit-cell of the hydrated uranyl diselenite has been determined from an indexed powder pattern: it crystallizes in the triclinic system with a = 9.40(4) A, b = 11.85(5) A, c = 6.69(5) A, ..cap alpha.. = 94.3(3)/sup 0/, ..beta.. = 90.3(3)/sup 0/, andmore » ..gamma.. = 114.5(3)/sup 0/, V = 676 A/sup 3/. On this basis, a structure derived from that of UO/sub 2/Se/sub 2/O/sub 5/ is proposed, corresponding to a reasonable packing of oxygen, water molecules, and lone pairs. 17 references, 7 figures, 3 tables.« less
  • The phase diagram of the Ag{sub 2}Se-Ho{sub 2}Se{sub 3} system in the range of 0-50mol.% Ho{sub 2}Se{sub 3} was constructed with the results of XRD and differential thermal analysis. A dimorphous compound exists in the system at the equimolar ratio of the components. The investigated part of the Ag{sub 2}Se-AgHoSe{sub 2} diagram is of the eutectic type with the eutectic coordinates 7mol.% Ho{sub 2}Se{sub 3} and 1125K. The crystal structure of the high-temperature modification of AgHoSe{sub 2} was studied by X-ray powder diffraction method. {alpha}-AgHoSe{sub 2} is described as a NaCl structure (space group Fm3-barm) with the lattice parameter a=5.7623(3)A.more » Atomic parameters were calculated in the isotropic approximation (R{sub I}=0.0434 and R{sub P}=0.0636). The crystal structure of {beta}-AgHoSe{sub 2} was determined by X-ray structure analysis and was refined to R=0.0487.« less
  • The quasi-ternary system Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} was investigated by differential thermal, X-ray phase, X-ray structure, microstructure analysis and microhardness measurements. Five quasi-binary phase diagrams, six polythermal sections, isothermal section at 820 K and the liquidus surface projection were constructed. The character and temperature of the invariant processes were determined. The specific resistance of the single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} was measured, 7.5×10{sup 5} and 3.15×10{sup 5} Ω m, respectively, optical absorption spectra in the 600–1050 nm range were recorded at room temperature, and the band gap energy was estimatedmore » which is 1.95±0. 01 eV for both samples. - Graphical abstract: The article reports for the first time the investigated liquidus surface projection of the Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system and isothermal section at 820 K of the system. Five phase diagrams, six polythermal sections, isothermal section at 820 K and the liquidus surface projection were built at the first time. The existence of the large region of the solid solutions based on AgIn{sub 5}Se{sub 8}, Ga{sub 2}Se{sub 3} and AgGa{sub 1−x}In{sub x}Se{sub 2} was investigated. The existence of two ternary phases was established in the Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system. Two single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} were grown and some of optical properties of them were studied at first time. Display Omitted - Highlights: • Liquidus surface projection was built for Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system. • Solid solution ranges of AgIn{sub 5}Se{sub 8}, Ga{sub 2}Se{sub 3} and AgGa{sub 1−x}In{sub x}Se{sub 2} were investigated. • Two single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} were grown. • Some optical properties of these single crystals were studied.« less
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