Ponomarenko T. Systems of cesium, lithium and yttrium chlorides with low concentration of oxygen-containing admixtures: synthesis and scintillation properties.

The work is devoted to the development of scientific basis of purification of melts based on alkali and rare earth chlorides from oxygen-containing admixtures by acid-base and Red-Ox methods. The oxobasicity indices of melts of CsCl-LiCl-YCl3 system were determined us-ing the direct method proposed in the frames of this work. The increase of concentra-tion of the most acidic cation of the melt was shown to cause the strengthening of its acidity. In Li2O is the prevailing form of oxide ions fixation is CsCl-LiCl system and the main form in CsCl-LiCl-YCl3 system is YO+. Using the obtained acidity parameters the features of running processes of purifi-cation of melts based on alkali and rare earth chlorides from oxygen-containing admix-tures by acid-base (action of HCl) and red-ox (action of Cl2 or CCl4) methods of purifi-cation. The limit residual concentrations of the admixtures for each method are esti-mated. The titrimetric method of determination of total oxygen-containing admixture concentration in halide materials was developed. The kinetics of molten 2 CsCl-LiCl-YCl3 carbohalogenation was studied and reaction order and the rate constant at 700 C are found. According to the developed routines single crystals of prospective neutron detec-tors based on complex alkali and rare earth chlorides (Cs2LiYCl6:Ce3+, Cs2LiYCl5Br:Ce3+, Cs2LiYBr6:Ce3+) and YCl3:Ce3+, YBr3:Ce3+ solid solutions were grown. The dependence of scintillation properties of the obtained materials vs. Ce3+ concentration was studied.