Abstract
Studies of the layered ferroelectric TlInS2 with an incommensurate phase at hydrostatic pressure (p atm≤p≤660 MPa) were performed. Based on the results of temperature dependence of the dielectric constant and dielectric loss, pyroelectric coefficient and spontaneous polarization at different pressures, a (p, T) phase diagram is obtained. A complex polycritical region is found in the range of 580≤p<660 MPa.