Analysis of structural transformation in nanocrystalline Y2O3 during high energy ball milling

Abstract

In-depth understanding of the structural transformation mechanism in nanocrystalline yttria (Y2O3) is crucial to design advanced materials satisfying a wide range of technical demands. Present study investigates the structural modification in cubic Y2O3 nanopowders induced by high energy ball-milling as a function of milling duration. Y2O3 nanopowder with an initial crystallite size of 25–50 nm was subjected to high energy ball milling (1000 rpm) for incremental time periods up to 30 h. X-ray diffraction (XRD) and Rietveld analysis were employed to study the phase evolution, crystallite size, and strain at every stages of milling. High Resolution Transmission Electron Microscopy (HR TEM) and Electron Energy Loss Spectroscopy (EELS) is utilized to realize the mechanisms involved in phase transformation. It is observed that as milling duration progresses, the cubic Y2O3 gets refined and gradually transforms to the monoclinic phase. It is also apparent that at finer sizes, the monoclinic phase is preferred over the cubic one. The critical crystallite size for the monoclinic phase to stabilize is observed to be ~ 13 nm. Results show the complete structural modification after 30 h of milling duration.