Journal of Crystal Growth, Vol.311, No.3, 921-924, 2009
Growth and magnetic characterization of high-quality alpha'-Na0.75CoO2 single crystals
The growth of high-quality alpha'-phase of Na0.75CoO2 single crystals was carried out by the floating zone method. Study of XRD and polarized optical microscopy was performed throughout the as-grown crystal ingot. The size of crystal grains is observed to improve gradually with the growth length. The entire ingot appeared to be one large crystal grain approached at similar to 8cm measured from the initial growth position. The homogeneous composition of Na0.90CoO2 and Na0.33CoO2 could be achieved by the Na de-intercalation of the as-grown crystal. A sharp Neel phase transition occurred at T-N similar to 22 K for Na0.75CoO2, Susceptibility data indicate pronounced metal-insulator transitions T-c at 53 and 88K for the Na0.90CoO2 and Superconducting transition of T-c similar to 4.8K for the hydrated Na0.33CoO2 center dot 1.3H(2)O. (C) 2008 Elsevier B.V. All rights reserved.