In semiconductors TlInS₂ the ferroelectric phase transition involves participation of an intermediate incommensurate phase. At the present, this incommensurate phase is an object of intensive investigation, since the relaxor peculiarity of materials caused by macrodomain-nanodomain transition is observed exactly in this phase. For many practical applications it is desirable to move this incommensurate phase, with its macrodomain-nanodomain transition, to higher temperatures.

In this paper we report the experimental results evaluating the influence of different cationic impurities on the phase transitions in TlInS₂ crystals. We have determined the dependence of the phase transitions on the impurity atom radius. This was done observing the dielectric constant temperature dependencies of TlInS₂ crystals doped by 0.1 atomic percent of Cr, Mn, Yb, Sm, Bi, and La. It has been established that Mn and Cr substitute In in the crystal lattice of TlInS₂. The atoms of other dopants occupy the octahedral interstices and lead to the translation of phase transitions into the high-temperature range.