Structural properties of CaCu3Ti4O12 obtained by mechanical alloying

Mechanical alloying has been used successfully to produce nanocrystalline powders of CaCu3Ti4O12 (CCTO), for the first time, using two different experimental procedures. The milled CCTO were studied by X-ray powder diffraction, infrared and Raman scattering spectroscopy. For two different milling procedures, CCTO was obtained after a couple of hours of milling (in average 30 h of milling, depending on the reaction procedure). The X-ray diffraction (XRD) patterns indicate that the crystallite size is within the range of 20-35 nm. After 100 h of milling the formation of CCTO was confirmed by X-ray powder diffraction in both procedures, with good stability. We also prepare the CCTO ceramic using the traditional procedure described in the literature and compared the physical properties of these samples with those ones obtained by milling process and good agreement was observed. The infrared and Raman scattering spectroscopy results suggest that the increase of the milling time leads to the formation of nanocrystalline CCTO, as seen by XRD analysis. These materials are attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones for example), where the decrease of the size of the devices are crucial. This milling process presents the advantage that melting is not necessary and the powder obtained is nanocrystalline with extraordinary. mechanical properties. The material can be compacted and transformed in solid ceramic samples or used in others procedures of film preparation. The high efficiency of the process opens a way to produce commercial amount of nanocrystalline powders. Due to the nanocrystalline character of this powder, their mechanical properties have changed and for this reason a pressure of 1 GPa is enough to shape the sample into any geometry. (C) 2002 Elsevier Science B.V. All rights reserved.