LASER-INDUCED TIME-RESOLVED SPECTROSCOPY OF VISIBLE BROAD LUMINESCENCE BANDS IN ZIRCON

Abstract

This work examines the luminescence of zircon studied by laser-induced time-resolved methods. This method allows the differentiation between luminescence centers of similar emission wavelengths, but different decay times. Samples include a suite of natural zircons, nominally pure synthetic ZrSiO4, and ZrSiO4 artificially doped by Mn, Fe, Cr, Ni, Co, Pb, Sb, Ti, Ta, V, Sc, U, U-P, and Th-P. In addition, pure ZrSiO4 samples irradiated by thermal neutrons have been studied. We have clarified the nature of several luminescence bands reported previously from time independent studies, and suggest the following as the causes of luminescence in zircon systems: 1) the yellow band with peak wavelength (λmax) = 575 nm, peak half-width (Δ) = 120–130 nm, and decay time (τ) = 30–35 µs is connected with neutron and alpha irradiation, 2) the green band with λmax = 505 nm and vibrational structure is linked to the presence of the uranyl ion, but it is only observed in artificial samples with co-doping by U and P, 3) the red band with λmax = 750 nm, Δ = 110–120 nm and τ = 3–5 ms is connected with Fe3+. We have also identified new luminescence bands, obscured by stronger emissions. These are: emission a) with λmax = 480 nm, Δ = 70–80 nm and τ = 300–325 µs, emission b) with λmax = 515 nm, Δ = 90–100 nm and τ = 500–520 µs, emission c) with λmax = 605 nm, Δ = 110–125 nm and τ = 8–10 µs. These emissions have not been detected in synthetic doped zircons and their interpretation remains the subject of further investigation.