The influence of mechanical activation on structural evolution of nanocrystalline SrTiO3 powders

Abstract

Structural changes caused by mechanical activation of SrTiO3 powders were investigated using a variety of methods. Average crystallite size continuously decreased with increased activation time to around 20 nm after 120 min activation, while mesopore volume and specific surface area increased accordingly. Higher activation times lead to increased agglomeration of nanoparticles to form agglomerates of around 2 mu m in size, ultimately producing a relatively stable powder, which exhibits lower microstrain than powders activated for shorter periods of time. Raman spectroscopy shows that the behavior of TO2 and TO4 modes is consistent with a decrease in particle size, while behavior of the nonpolar TO3 mode is markedly different, indicating relaxation of the inversion symmetry in polycrystalline SrTiO3. UV-VIS spectra show that mechanical activation has negligible effect on SrTiO3, with a slight shift caused by TiO2 contamination due to presence of air. Other than this, the mechanical activation process preserves the chemical purity of the initial powder.