Polytypes in ferroelectric TlInS2 and its dielectric and optic properties

Abstract

AbstractPolytypes (Ps) of monoclinic TlInS2 with lattice parameters c (c ≈ 15 Å, c ≈ 30 Å, c ≈ 60 Å, c ≈ 120 Å and c ≈ 240 Å) have been obtained by long time annealing in vacuum or in sulfur vapour (P c ≈ 240 Å) of TlInS2 crystal at different temperatures‐T. From the temperature dependence of dielectric constant ϵ (T) of pure Ps it is established, that well known ferroelectric phase transition (FPT) in TlInS2 takes place with single peaks of dielectric anomaly (DA) at slightly different temperatures for different Ps. Samples with pure P are unstable and are returning to mixed Ps state again after some time. The most unstable is the P with c ≈ 15 Å. It is shown that FPT and optic measurements can be used as Ps analysis methods in TlInS2 samples. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)