Color and photo-luminescence of rare earth element-doped zircon.

Abstract

Absorption and photo-luminescence spectra of synthetic zircons doped with rare earth elements (REE) have been examined using a polarizing microscope spectrophotometer. Zircons containing each one of Tb2+, Tm3+, Ho3+ and Er3+ ions show characteristic absorption in the visible region, and the latter three ions in the zircon crystal give also peculiar photo-luminescence bands with enhanced intensities compared with their absorption bands. Although the zircons containing REE except the above four ions do not give any absorption bands in this region, Dy3+, Eu3+, Sm3+ and Pr3+ ions have emitted the characteristic photo-luminescence whose intensities are enhanced in the zircon crystal. Relative intensities of those luminescences decrease in the order of Dy, Tm, Eu, Sm, Er, Ho and Pr under UV-excitation. These luminescence bands are due to the well-known 4f–4f electron transitions within REE. Trivalent Sc in zircon crystal can also emit the luminescence, where the luminescent center may be formed in the forbidden band of the zircon. The other REE (Y, La, Ce, Nd, Gd, Yb and Lu) do not have any characteristic luminescent and absorption bands in the visible region.The results are applied to assign the optical bands observed in natural zircons. Trivalent ions such as Dy, Tm, Eu and Sm are identified in the luminescence spectra under the microscope. While the other ions are not detected in both absorption and luminescence spectra of the zircon in this study.