Effect of Calcination Condition on Phase Formation Characteristics of NdBa2Cu3Oy Powder Prepared by Solidstate Reaction

Abstract

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 850-920C and, thereafter, the sample melted. The calcination process of Nd-123 compound was carried out by heating the starting precursors at 800-950C 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 900C. 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 900C 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 1.160.33 μm to 31.72 9.27 μm. The result of fitting the XRD pattern showed that the sample re-calcined at 900C for 24 h exhibited increased weight fraction of Nd-123 with minimized concentration of secondary phases.