Low-temperature hydrothermal synthesis of the three-layered sodium cobaltite P3-NaxCoO2 (x ∼ 0.60)

Marinela Miclau (1) , Kumar Bokinala Kiran (2, 1, 3) , Nicolae Miclau (3)

1 National Institute for R&D in Electrochemistry and Condensed Matter
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 UPT - Universității Politehnica Timișoara [România] = Polytechnic University of Timişoara [Romania] = Université polytechnique de Timișoara [Roumanie]

In order to obtain the layered sodium cobalt oxide materials by hydrothermal synthesis, the yield diagram for Na–Co–H2O system has been built and studied. In the same time, the well-known data of Co–H2O system have been extended at 250 °C in basic solution.We had first synthesized directly the high temperature stable phase, P3-Na0.6CoO2P3-Na0.6CoO2 by a one-step low-temperature hydrothermal method. The rhombohedral structure of P3-Na0.6CoO2P3-Na0.6CoO2 has been determined by X-ray diffraction (XRD) and the purity of phases has been confirmed by XPS. The thermal stability of P3-Na0.6CoO2P3-Na0.6CoO2 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-Na0.6CoO2P3-Na0.6CoO2 in the rhombohedral stable phase α-NaCoO2α-NaCoO2 (space group R-3m ) was observed. Also, a formation mechanism of P3-Na0.6CoO2P3-Na0.6CoO2 phase using the unit cell theory in the hydrothermal process was proposed.

Mots clés: Layered compounds; Phase equilibria; Photoelectron spectroscopy; X-ray diffraction

Domaines: Matériaux

Marinela Miclau, Kumar Bokinala Kiran, Nicolae Miclau. Low-temperature hydrothermal synthesis of the three-layered sodium cobaltite P3-NaxCoO2 (x ∼ 0.60). Materials Research Bulletin, 2014, 54, pp.1-5. ⟨10.1016/j.materresbull.2014.02.018⟩. ⟨hal-01088675⟩