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Title: Low-temperature hydrothermal synthesis of the three-layered sodium cobaltite P3-Na{sub x}CoO{sub 2} (x ∼ 0.60)

Highlights: • We report direct synthesis of the high temperature stable phase, P3-Na{sub 0.6}CoO{sub 2}. • The hydrothermal synthesis of P3-Na{sub 0.6}CoO{sub 2} involves one step and low temperature. • The yield diagram for Na–Co–H{sub 2}O system has been builded up to 250 °C. • We propose a formation mechanism of P3-Na{sub 0.6}CoO{sub 2} phase using the unit cell theory. • The thermal stability of P3-Na{sub 0.6}CoO{sub 2} has been investigated by means of HT-XRD. - Abstract: In order to obtain the layered sodium cobalt oxide materials by hydrothermal synthesis, the yield diagram for Na–Co–H{sub 2}O system has been built and studied. In the same time, the well-known data of Co–H{sub 2}O system have been extended at 250 °C in basic solution. We had first synthesized directly the high temperature stable phase, P3-Na{sub 0.6}CoO{sub 2} by a one-step low-temperature hydrothermal method. The rhombohedral structure of P3-Na{sub 0.6}CoO{sub 2} has been determined by X-ray diffraction (XRD) and the purity of phases has been confirmed by XPS. The thermal stability of P3-Na{sub 0.6}CoO{sub 2} has been investigated by means of high temperature X-ray diffraction in 298–873 K range and when the temperature has reached 723 K, the completely transformation of P3-Na{sub 0.6}CoO{submore » 2} in the rhombohedral stable phase α-NaCoO{sub 2} (space group R-3m) was observed. Also, a formation mechanism of P3-Na{sub 0.6}CoO{sub 2} phase using the unit cell theory in the hydrothermal process was proposed.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4]
  1. National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, 1 Plautius Andronescu, 300224, Timisoara (Romania)
  2. (France)
  3. (Romania)
  4. Politehnica University of Timisoara, Pta Victoriei No. 2, 300006, Timisoara (Romania)
Publication Date:
OSTI Identifier:
22348654
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 54; Other Information: Copyright (c) 2014 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; COBALT OXIDES; HYDROTHERMAL SYNTHESIS; IMPURITIES; PHASE DIAGRAMS; SODIUM; SOLUTIONS; SPACE GROUPS; TRIGONAL LATTICES; WATER; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY