Structural differences existing in bulk and nanoparticles of Y2Sn2O7: Investigated by experimental and theoretical methods

Present manuscript deals with the structural changes associated with transformation of bulk Y2Sn2O7 into nanoparticles of Y2Sn2O7. Nanoparticles of Y2Sn2O7 both undoped and Eu3+ doped, were prepared at a relatively low temperature (700 °C) and investigated for their structural and luminescence properties and compared them with that of bulk Y2Sn2O7 sample prepared by the solid-state method at 1300 °C. Significant distortion in geometry and electron density distribution around Y3+/Eu3+ ions in nanoparticles are confirmed from the Rietveld refinement of the powder X-ray diffraction patterns and theoretical calculations based on the density functional theory (DFT). The SnO6 octahedron in Y2Sn2O7 is more expanded in nanoparticles compared to bulk. Iso-surface density distribution reveals that while bulk sample shows typical ionic feature in Y/EuO bonds, nanoparticle sample shows sharing of electron density along bond axis pertaining to covalent character. These inferences are further supported by the doped Eu3+ luminescence and calculated Ω2 and Ω4 parameters.