The influences of monovalent ions on the stability of scintillation properties and radiation hardness of PbWO4 : Y3+ crystals

摘要

Some Y3+-doped PbWO4 crystals grown by modified Bridgmann method showed exceptional behaviors, namely, light yield increased after low dose rate irradiation, and the radiation-induced absorption coefficient was negative around 430 nm, In this paper, the influences of monovalent ion impurities (Na+ and K+) on the stability of scintillation properties and radiation hardness were studied. The experimental results show that Na+ ion enhances the absorption band at cut-off edge and at 430 nm, while K+ ion only makes optical transmission unstable around 430 nm when the crystals were annealed at high temperatures. The contamination by Na+ and K+ ions makes scintillation properties and radiation hardness more unstable in the temperature range from 50degreesC to 350degreesC. The radiation-induced absorption coefficient is also negative around 430 nm, The charge compensation mode of K+ ion. along the crystal does not change, but those of Na+ ion are different along the crystal. The concentrated Na+, K+ and Y3+ ions, which occupied Pb sublattice, lead to the shortage of Pb vacancies (V-Pb"). Thus instead of the formation of 2(Y-Pb(3+))(circle)-V-Pb" ((Y-Pb(3+))(circle) Pb Pb stands for the Y3+ ion occupying the Pb sublattice), Na+ and K+ ions compel the defect (Y-Pb(3+))(circle) to form cluster 2(Y-Pb(3+))(circle)-O-i" or (Y-Pb(3+))(circle) 2(Y-Pb(3+))(circle)-O-i" or (Y-Pb(3+))(circle)-O-i" + hole in which the interstitial oxygen (O-i") was considered to be the origin of light yield increase after low dose rate irradiation. (C) 2002 Elsevier Science B.V. All rights reserved. References: 27