The present paper shows the results of complex experimental studies of optical phenomena, electron-paramagnetic resonance, Raman scattering, and heat capacity in TlGaS2 single crystals doped with various concentrations of rare-earth (RE) ions. The autore were the first to discover that optic parameters of TlGaS2 single crystals can be improved by increasing the degree of structural ordering of the cation sublattice doping them by RE ions. The impurity ions with the ionic radii close to the radii of the main cations (Tl3+, Ga3+) and charges of main cations in the area of rather low concentrations were shown to exert an ordering effect on the cation sublattice of a congruent TlGaS2 crystal.
In this case the crystal resistance to laser radiation is also observed to grow. The effect of diminishing photorefraction while the crystal is doped, apparently, dul to increasing efficiency of the radiating recombination of photo-excited carriers without their being captured to deeper levels, and correlates well with the discovered ordering of the cation sublattice and both of them are observed for the same, relatively narrow, range of concentrations and the type of doping impurities. The efficiency of such a recombination determines the intensity of luminescence in doped crystals. And greater luminescence is attained by alloying them in the concentration range of RE, ions in which the alloyed single crystals possess the maximum degree of structural ordering and increased resistance to optic damage.