Non-monotonic lattice parameter variation in ball-milled ceria

High-energy ball milling is utilized in creating microstructural changes (such as change in lattice parameter, lattice strain) within micro-ceria, which were quantified using line profile analysis by X-ray diffraction. Crystallite size significantly decreased from 85 to 11 nm when subjected to 4 h of high-energy ball milling, and then remained same with increase in milling duration (up to 16 h of milling). Three different methods, namely Nelson–Riley function, Cohen’s method, and Pawley fitting, were used to calculate the lattice parameter and a lattice expansion from 5.4082 to 5.4147 A was observed for a duration of 0 up to 12 h. The effect of milling on generation of residual strain and the probability of stacking fault in affecting the lattice parameter are delineated in the current work. Non-monotonic change of lattice parameter with saturation of crystallite size is attributed to the vacancy-induced stresses that generate at inter-crystallite regions and render excessive free volume during high-energy ball milling.