In this article, effect of Sn on the electrical, optical, and thermal properties of Ge2Sb2Te5 is studied. Ge2Sb2Te5, Ge1.55Sb2Te5Sn0.45, and Ge1.1Sb2Te5Sn0.9 alloys are prepared by melt quenching technique and their thin films are prepared by thermal evaporation on glass substrates. These materials are then characterized by differential scanning calorimetry, X-ray diffraction, optical method, and impedance measurements. Doping with Sn maintains the NaCl-type crystalline structure of Ge2Sb2Te5. Activation energy (E (a)) for crystallization is calculated by Kissinger's method. E (a) decreases slightly from 2.56 eV for Ge2Sb2Te5 to 2.24 eV for Ge1.1Sb2Te5Sn0.9. The distinct change in extinction coefficient (k) of Ge2Sb2Te5 and Sn-doped amorphous films is found in the visible region. A large increase in optical contrast (C) is observed in the Sn-doped phase change materials. The phase change transition is studied using impedance measurements as a function of temperature. Impedance measurements show the appearance of nucleation centers in samples heated at temperatures below crystallization temperature (T (c)) and above glass transition temperature (T (g)).