Estimation of lattice strain and optical properties of scheelite-type AWO4 (A = Ca, Sr, Ba) nanocrystalline materials synthesized by mechanical activation

We report the estimated lattice strain and optical behavior of Scheelite-type AWO4 (A=Ca, Sr, Ba) nanocrstalline synthesized by mechanical activation. The X-ray diffraction patterns of the synthesized samples were analyzed by Rietveld refinement. Rietveld refinement confirms that the structure of the AWO4 (A=Ca, Sr, Ba) nanocrystallite samples are tetragonal with the space group I41/a. The lattice constants, unit cell volume and tetragonality of the AWO4 samples increase with increasing ionic radii of A-site cation. Average values of crystallite size and lattice strain were estimated using Williamson-Hall method. The direct band gap of the Scheelite-type AWO4 samples increases with increase in ionic radii of A-site cations.