Laser-induced time-resolved spectroscopy of visible broad luminescence bands in zircon

摘要

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 ZrSiO_4, and ZrSiO_4 artificially doped by Mn, Fe, Cr, Ni, Co, Pb, Sb, Ti, Ta, V, Sc, U, U-P, and Th-P. In addition, pure ZrSiO_4 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 (lambda_(max)) = 575 nm, peak half-width (DELTA) = 120-130 nm, and decay time (tau) = 30-35 mu s is connected with neutron and alpha irradiation, 2) the green band with lambda_(max) =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 lambda_(max) =750 nm, DELTA=110-120 nm and tau= 3-5 ms is connected with Fe~(3+). We have also identified new luminescence bands, obscured by stronger emissions. These are: emission a) with lambda_(max)=480 nm, DELTA=70-80 nm and tau=300-325 mu s, emission b) with lambda_(max)= 515 nm, DELTA = 90-100 nm and tau = 500-520 mu s, emission c) with lambda_(max) =605 nm, DELTA =110-125 nm and tau =8-10 mu s. These emissions have not been detected in synthetic doped zircons and their interpretation remains the subject of further investigation.