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Title: Low Temperature Phases of Na 2Ti 3Cl 8 Revisited

Abstract

Here, the low temperature phases of Na 2Ti 3Cl 8 and their phase transitions were investigated by powder neutron diffraction, heat capacity, and magnetic susceptibility measurements between 1.6 K and room temperature. Aside from the previously known high temperature α-phase ( R3m) and low temperature γ-phase ( R3m), a new intermediate temperature β-phase was detected. It has a k = (1/4,1/4,0) superstructure and its molar volume and χT product are half way between the α- and γ-phases. The β-phase is observed between 210 K and 190 K on cooling in powder samples. Its formation is kinetically hindered in crystals. Upon heating the β→α transition occurs at 227 K. From the γ-phase, a γ→α transitions is observed on heating. Only in heat capacity measurements, a shoulder of the peak indicates an intermediate formation of the β-phase. Strong antiferromagnetic interactions between the Ti 2+ ions result in the formation of triangular trimers (Ti 3 clusters). In the γ-phase all Ti 2+ ions are part of trimers. For the β-phase a structural model is proposed, where half of the Ti 2+ ions form trimers. No long-range magnetic order was observed in Na 2Ti 3Cl 8 down to 1.6 K.

Authors:
 [1]; ORCiD logo [2];  [1];  [3];  [1]
  1. Univ. of Bern, Bern (Switzerland)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1413617
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Zeitschrift fuer Anorganische und Allgemeine Chemie
Additional Journal Information:
Journal Volume: 643; Journal Issue: 23; Journal ID: ISSN 0044-2313
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Chlorides; Kagome lattice; Sodium salts; Titanium; Phase transitions

Citation Formats

Hanni, Nora, Frontzek, Matthias D., Hauser, Jurg, Cheptiakov, Denis, and Kramer, Karl. Low Temperature Phases of Na2Ti3Cl8 Revisited. United States: N. p., 2017. Web. doi:10.1002/zaac.201700331.
Hanni, Nora, Frontzek, Matthias D., Hauser, Jurg, Cheptiakov, Denis, & Kramer, Karl. Low Temperature Phases of Na2Ti3Cl8 Revisited. United States. doi:10.1002/zaac.201700331.
Hanni, Nora, Frontzek, Matthias D., Hauser, Jurg, Cheptiakov, Denis, and Kramer, Karl. Tue . "Low Temperature Phases of Na2Ti3Cl8 Revisited". United States. doi:10.1002/zaac.201700331.
@article{osti_1413617,
title = {Low Temperature Phases of Na2Ti3Cl8 Revisited},
author = {Hanni, Nora and Frontzek, Matthias D. and Hauser, Jurg and Cheptiakov, Denis and Kramer, Karl},
abstractNote = {Here, the low temperature phases of Na2Ti3Cl8 and their phase transitions were investigated by powder neutron diffraction, heat capacity, and magnetic susceptibility measurements between 1.6 K and room temperature. Aside from the previously known high temperature α-phase (R3m) and low temperature γ-phase (R3m), a new intermediate temperature β-phase was detected. It has a k = (1/4,1/4,0) superstructure and its molar volume and χT product are half way between the α- and γ-phases. The β-phase is observed between 210 K and 190 K on cooling in powder samples. Its formation is kinetically hindered in crystals. Upon heating the β→α transition occurs at 227 K. From the γ-phase, a γ→α transitions is observed on heating. Only in heat capacity measurements, a shoulder of the peak indicates an intermediate formation of the β-phase. Strong antiferromagnetic interactions between the Ti2+ ions result in the formation of triangular trimers (Ti3 clusters). In the γ-phase all Ti2+ ions are part of trimers. For the β-phase a structural model is proposed, where half of the Ti2+ ions form trimers. No long-range magnetic order was observed in Na2Ti3Cl8 down to 1.6 K.},
doi = {10.1002/zaac.201700331},
journal = {Zeitschrift fuer Anorganische und Allgemeine Chemie},
issn = {0044-2313},
number = 23,
volume = 643,
place = {United States},
year = {2017},
month = {10}
}