Study of the ferroelectric properties of Ge–Sb–Te alloys

Some physical, electrical and ferroelectric properties of Ge40SbxTe60−x   alloys where x=1x=1, 5 and 10 wt% as well as of Ge50Te50 in the bulk state were studied. The X-ray diffraction measurements show that all the prepared samples are in crystalline state. Differential thermal analysis measurements show that the melting point decreases when Sb replaces Ge or Te. All samples having Sb show a solid–solid (structural) transformation and ferroelectric–paraelectric transition. These transition temperature increases as Sb content increases. The DC electrical resistivity measurements on the other hand indicated that all samples show metallic behavior. Measurements of the dielectric constant as a function of temperature at frequency 1 kHz for Ge50Te50 sample give an indication that this material is a normal displacive ferroelectric showing first-order phase transition. Measurements of the polarization as a function of applied field for all samples at frequency of 60 Hz was found in good agreement with the Langevin function especially for Ge50Te50 and Ge40Sb5Te55 samples. The dielectric permittivity on the other hand shows for all samples a reversal nonlinear quadratic behavior as the applied electric field is increased.