Nowadays Li₆RE(BO₃)₃ (RE=Y, Eu, Gd, Yb) single crystals are intensively studied for different applications due to their promising optical properties. They belong to the monoclinic system, space group P2₁/c. Li₆Y(BO₃)₃ and Li₆Gd(BO₃)₃ crystals activated with erbium or ytterbium are considered as laser materials [1, 2]. Cerium activated Li₆Y(BO₃)₃ and Li₆Gd(BO₃)₃ crystals are prospective scintillation detectors for thermal neutrons registration [3]. Recently we have shown that Li₆Gd(Y)(BO₃)₃:Eu³⁺ possesses intense thermally stimulated luminescence (TSL). High TSL yield combined with high temperature of the main TSL peak and non-hygroscopicity allows one to consider these crystals as promising storage phosphors [4]. This work is devoted to develop a dosimetric material with variable value of effective atomic number Z_eff. on the basis of Li₆Gd_1-xY_x(BO₃)₃:Eu³⁺ solid solution and to determine their storage properties.

Peculiarities of phase formation in the Li₂O–B₂O₃–RE₂O₃ (RE=Gd, Y) systems have been studied by means of differential thermal analysis and X-ray phase analysis. The solubility in the binary system Li₆Gd(BO₃)₃–Li₆Y(BO₃)₃ has been determined. It has been shown that Li₆Gd_1-xY_x(BO₃)₃ solid solutions exist in all the concentration range of x values (sigar-like phase diagram). Pure and europium activated Li₆Gd_1-xY_x(BO₃)₃ single crystals up to 15 mm in diameter and up to 20 mm in length have been grown using Czochralski method in air atmosphere. The influence of the growth conditions and seed crystal orientation on the structural perfectness of obtained crystals has been analyzed. The main physico-mechanical properties of Li₆Gd_1-xY_x(BO₃)₃ crystals have been determined.

The models of charge carrier traps in Li₆Gd_1-xY_x(BO₃)₃:Eu³⁺ crystals have been proposed basing on the analysis of TSL, photoluminescence, thermal decoloration, and peculiarities of crystal structure. The possibility of practical application of Li₆Gd_1-xY_x(BO₃)₃:Eu³⁺ solid solutions with variable value of Z_eff. for solid state dosimetry have been discussed.

[1] J. Sablayrolles, V. Jubera, J.-P. Chaminade et al., Optical Materials 27 (2005) 1681.

[2] Y. Zhao, X. Gong, Y. Lin et al., Materials Letters 60 (2006) 418.

[3] J.P. Chaminade, O. Viraphong, F. Guillen, C. Fouassier and B. Czirr, IEEE Transactions on Nuclear Science 48 (2001) 1158.

[4] R.P. Yavetskiy, E.F. Dolzhenkova, M.F. Dubovik et al., Journal of Crystal Growth 276 (2005) 485.

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