STRUCTURE INVESTIGATIONS OF BI_5TI_3FEO_(15) CERAMICS PREPARED BY FREE SINTERING PROCESS OF HIGH-ENERGY BALL MILLED NANOCRYSTALLINE PRECURSORS

摘要

The tested material was prepared in two stages. In the first stage polycrystalline precursor material (mixture of Bi_2O_3, TiO_2 and Fe_2O_3 powders) was ground with the use of high-energy vibratory mill. The second stage was free sintering of ground precursor material conducted at 800 deg C/5 hours. The X-ray diffraction methods were applied for the structure characterization of the examined samples. The parameters of diffraction line profiles were determined by PRO-FIT Toraya procedure. The crystallite sizes and lattice distortions were analyzed using Williamson-Hall method. Investigations of hyperfine interactions in the studied materials were carried out by Mossbauer spectroscopy. The powder morphology was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. X-ray diffraction studies indicate the formation of Bi_5Ti_3FeO_(15) phase during high-energy ball milling of the precursor mixture of component oxides. Thus the phase transition proceeds during high-energy ball milling. Moreover decrease of crystallite size and amorphization process are observed. Electron microscopy observations point out the presence of crystalline phase and of amorphous one. X-ray diffraction pattern reveals the crystallization of only one, Bi_5Ti_3FeO15 phase during free sintering process.