Phase transformation and structural development in mechano-synthesized calcium-copper-titanate electroceramics

Abstract

This research focuses on the mechano-synthesis of synthesizing calcium-copper-titanate (CCTO) powder through mechanical alloying of the respective oxides aiming to optimize the production of nanoscale electroceramics with high dielectric properties. Structural characterization was carried out using X-ray diffraction with Rietveld refinement (phase identification and quantification), while transmission electron microscopy was employed to observe particle size changes including the reduction of particle size to nanometric scales (10–35 nm). The mechano-synthesis process involving CaO, CuO, and $TiO_2$ resulted in the creation of perovskite CCTO, with minimal contamination observed from the milling process. Significant particle size reduction, nanostructure formation, and a high level of amorphization, alongside polymorphic transitions in $TiO_2$ during milling that played a critical role in achieving full amorphization, which was essential for the formation of high-purity CCTO. The study demonstrates that after 256 h of milling, 88 wt% of the powder consisted of crystalline CCTO, highlighting the potential for enhanced performance in dielectric and microelectronic applications. There was no detection of either stoichiometric CCTO or any non-stoichiometric phases prior to the complete amorphization of the powders. Therefore, results revealing significant advancements in particle size reduction, nanostructure formation, and amorphization, which influence enhanced material performance. Nucleating and growing the CCTO phase directly from an amorphous state without the formation of intermediate crystalline phases clears the potential for optimizing CCTO production processes.