K(Sr1−xEux)2Cl5 scintillation material obtained using Eu2O3 dissolution in the growth chloride melt

Abstract

The peculiarities of direct incorporation of Eu2+ (via Eu2O3) in KCl-SrCl2 (1:1.99) melt for the growth of Eu2+-activated scintillation material of K(Sr0.995Eu0.005)2Cl5 composition were studied. When added to the chloride melt at 973 K Eu2O3 starts to transform into EuOCl immediately and the process is essentially incomplete. The complete dissolution of Eu oxocompounds (Eu2O3, EuOCl) in the melt was provided by the application of the carbochlorination process (the action of CCl4 vapor) which is a special case of the reactive atmosphere processing (RAP). A scintillation material of K(Sr0.995Eu0.005)2Cl5 composition was grown from the obtained melt with an application of the Bridgman technique. The boule included long opaque end sections and transparent medium section with the composition of K(Sr0.995Eu0.005)2Cl5. The luminescence studies of the obtained samples confirmed coexistence of both Eu2+ and Eu3+ in the growth melt. The non-isomorphic Eu3+ is displaced to the top section of the boule as a result of directional crystallization. An amount of KI was added to the growth melt to provide complete reduction of Eu3+ into Eu2+. Scintillation parameters of all the obtained crystals are close: the relative light yield values are ca.70% vs. NaI:Tl and the energy resolution is within 8–9%.