Peculiarities of doping KBr-2SrBr2 melt with europium at 973 K

The processes of Eu2O3 solubilization in molten KBr-2SrBr2 at 973 K were studied from the viewpoint of introducing rare-earth dopants in melts in situ for obtaining activated halide scin-tillators. The control of the solubilization was performed on the basis of current oxide-ion mo-lality (mO2-) which was detected by the potentiometric method. A membrane oxygen electrode Pt(O2)|YSZ was used as an indicator one. The process of Eu2O3 solubilization in KBr-2SrBr2 melt with the formation of Eu2+ does not occur due to slight solubility of EuO or EuOBr. The solubil-ity product of EuO in the studied melt is estimated as 2.8 10-7 mol2 kg-2. The carbohalogenation process (treatment with 'C+Br2' red-ox couple) provides not only the dissolution of oxide, but also complete Eu3+-Eu2+ reduction. The kinetic study of the carbohalogenation process in KBr-2SrBr2 melt containing suspension of Eu oxocompounds show that in this case the plateau-like section arises in 'pO-time' dependences due to participation of two solid substances (carbon and Eu oxo-compounds) in the reaction. The data corresponding to the end of this plateau-like section give another option to estimate the solubility product of EuO as 1.6 10-7 mol2 kg-2 that is in a good agreement with the above value (taking into account the experimental errors). The dissolution of Eu2O3 (at the addition of mEu 2O3 = 5 10-3 mol kg-1) is finished in 40 min and the total deoxi- dization process is finished in 90 min whereas in the reference experiment the duration of the deoxidization of 'pure' melt is 50 min.