Journal of Physical Studies 3(2), 199–204 (1999)
DOI: https://doi.org/10.30970/jps.03.199

THERMO-INDUCED TRANSFORMATIONS OF COLOUR CENTRES IN SrCl2–Tl+–Na+ CRYSTALS

A. S. Krochuk1, Z. P. Chorniy2, G. O. Shchur2, V. M. Salapak2, N. V. Hovor1
1The Ivan Franko State University of Lviv
50, Drahomanov Str., Lviv, UA-290005, Ukraine,
1 Ukrainian State University of Forestry and Wood Technology
103, Gen. Tchuprynka Str., Lviv, UA-290057, Ukraine

The impurities of thallium and sodium are included into the SrCl$_2$ crystal lattice as Tl$^+V_a^+$ and Na$^+V_a^+$ impurity–vacant dipoles. Low–temperature irradiation of SrCl$_2$–Tl$^+$-Na$^+$ crystals generates electronic Tl$^oV_a^+$ and Na$^+V_a^o$ and hole Tl$^{2+}V_a^+$ and Na$^+V_a^+e_s^+$ colour centres. Thermo–induced transformations of ‟thallium" and ‟sodium" colour centres take place independently and parallel to each other. The transformation of ‟thallium" colour centres is based on the ionic mechanism ($ \{$Tl$^oV_a^+$–Tl$^{2+}V_a^+\} → \{$Tl$^o\cdot 2V_a^+$–Tl$^{2+}\}$), and the ‟sodium" one — on both ionic and electronic–hole ($\{ F_{\rm{A}}-V_{\rm{KD}}\}→\{ M_{\rm{A}}^+-V_{\rm{KA}^-}\}$). Only at $T >$ 250 K, when $F$–centres become mobile, an interaction of the latter with Tl$^o\cdot 2V_a^+$–centres occurs. However, the efficiency of this reaction is insufficient and does not change the concentration of ‟thallium" colour centres to a considerable extent.

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