Dipolar glass phase in ferrielectrics: CuInP2S6 and Ag0.1Cu0.9InP2S6 crystals

The dielectric properties of CuInP2S6 and Ag0.1Cu0.9InP2S6 crystals were investigated in wide frequency (20 Hz–3 GHz) and temperature ranges (25–360 K). The low frequencies dielectric spectra at high temperatures are highly influenced by the high ionic conductivity. The temperature dependences of the static dielectric permittivity and the mean relaxation time reveal the first order order–disorder ferrielectric phase transition at Tc = 288 K in Ag0.1Cu0.9InP2S6. The conductivity and its activation energy exhibit only a weak change close to the ferrielectric phase transition temperature in both investigated crystals. The freezing phenomena in CuInP2S6 and Ag0.1Cu0.9InP2S6 revealed the complex dielectric permittivity behaviour characteristic for transition into dipolar glass state.