Crystal structure and XANES study of Sn-substituted YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-y</inf> powder prepared by solid-state synthesis method

Abstract

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature. In this research, the crystal and chemical characterizations of Sn-substituted YBa2Cu3O7-y (YBCO) powder were studied. The experimental powder samples of (Y1-xSnx)Ba2Cu3O7-y (0 ≤ x ≤ 0.2) were prepared using the solid-state synthesis method. The starting precursor powders in appropriate ratios were mixed and calcined at 880 °C for 12 h in a normal atmosphere. The calcined powders were investigated for phase content using the X-ray diffraction technique (XRD). The microstructure of the powders was investigated by scanning electron microscopy (SEM). The chemical composition was carried out by energy-dispersive X-ray analysis (EDX). In addition, the details of the oxidation state of Sn and Cu determined by X-ray absorption near-edge structure (XANES) spectroscopy was also analyzed and discussed in relation to the cationic site substitution and variation in the local structure. It was found that the indexing of the XRD pattern showed Sn-substituted YBCO main peaks, and the impurity peaks of BaSnO3 and BaCuO2 were also found in the pattern. The small solubility of Sn in YBCO matrix was the major factor which induced the formation of the latter secondary phase. SEM images of the particles indicated that they possessed an irregular shape with a particle-size range of 1–3 μm. Sn L3-edge XANES spectra indicated that the average formal valence of Sn was Sn2+/Sn4+. The Cu K-edge spectra helped confirm that the Sn ions could not substitute Cu site in YBCO structure.