An interpretation of the optical properties of Cr4+-activated pyrochlores, Y2Ti2O7 and Y2Sn2O7

A qualitative model is proposed to explain the differences between the optical properties of the six-coordinated Cr4+ ion in the pyrochlores, Y2Sn2O7 and Y2Ti2O7. It is shown that polarization of the electron density of the oxygen ions occupying the 48f sites of the pyrochlore lattice is responsible for the observed differences in the optical properties.