SH. NUROV (a), V. M. BURLAKOV (a), E. A. VINOGRADOV (a), N. M. GASANLY (b), and B. M. DZHAVADOV (b)Structural phase transitions in TlInS,, TlIno,9~Gao~05S,, and TlIn(So,8Seo,,), crystals are investigated by infrared reflection spectroscopy. An attempt is made to affect the parameters of the vibrational spectrum and the phase transition temperatures of a TIInS, crystal by introducing impurities into it in order to obtain additional data necessary to construct phase transitions mechanisms. ~CCJW~OBaHbI CTpYKTYpHbIe (Pa30Bbxe nepexoAb1 B IipWCTannaX TIInS,, TlIq,,,,Ga~,05S, EI T11n(Seo,zSo,s)8 MeTonoM cnewrpocHonm mQpaKpacHoro oTpamemrr. npti IIOMOWH ero ~0ne6a~enb~01-0 cnempa EI TeMnepaTypbx Qaaosbrx nepexoAoB, T e M caMbiM, 11ony-BBeAeHHH IIpMMeCefi B HpHCTaJIn TIInS, CAeJIaHa IIOIIblTKa B03AeRCTBOBaTb Ha IIapaMeTpbX 9MTb AOIIOJIHkiTenbHbIe AaHHble &JIH IIOCTpOeHMH MeXaHMI3MOB (pa30BbIX lIepeXOAOB. l ) Lumumbastr. 23, 370602 Baku, USSR.?) An exception is the TlInSe, crystal whose group of symmetry is likely to be D:f,.