Effect of calcination condition on phase formation characteristics of NdBa<inf>2</inf>Cu<inf>3</inf>O<inf>y</inf> powder prepared by solid-state reaction

Abstract

© 2020, Chiang Mai University. All rights reserved. The article details the solid-state synthesis of Nd-123 powder under a normal air atmosphere using a stoichiometric ratio (i.e. Nd:Ba:Cu = 1:2:3) of high-purity Nd2O3, BaCO3 and CuO starting powders. The as-calcined powder was analyzed using thermo-analytical (DSC/TGA) techniques. The exotherm was related to the formation of Nd-123 which occurred around 850-920oC and, thereafter, the sample melted. The calcination process of Nd-123 compound was carried out by heating the starting precursors at 800-950°C for 12 h. Phase identification was determined using an X-ray diffractometer (XRD) and the quantitative phase analysis was performed by fitting the XRD pattern using the GSAS-II program. The morphology was observed by scanning electron microscopy (SEM) with chemical composition identification from EDS mode. The result of XRD showed that NdBa2Cu3Oy (Nd-123) was identified as the main crystalline phase along with other minor secondary phases when the calcination temperature was 900oC. The approximated stoichiometry of the powder was Nd:Ba:Cu = 1:2.09:3.16, which was very close to the expected nominal composition. Therefore, the calcination temperature at 900°C was selected for further synthesis study by varying the calcination time (12, 18, 24 and 30 h). Particle size analysis indicated that the powders were consisted of irregular-shaped particles linked together to form agglomerates. The particle size tended to increase with increasing time of calcination process with a size range from 1.16±0.33 µm to 31.72 ±9.27 µm. The result of fitting the XRD pattern showed that the sample re-calcined at 900oC for 24 h exhibited increased weight fraction of Nd-123 with minimized concentration of secondary phases.