Macroscopic phase separation of Se-rich (x < 1/3) ternary Ag_y(Ge_xSe_1−x )_1−y glasses

Temperature modulated differential scanning calorimetry measurements on Ag_y(Ge_xSe_1−x) _1−y glasses provide evidence for bimodal glass transition temperatures in Se-rich glasses (x < 1/3). At x = 0.20 and 0.25, thermal measurements performed as a function of Ag content in the 0 ≤ y ≤ 0.25 range reveal that the additive (Ag) segregates into an Ag₂Se-rich glass phase, possessing a characteristic glass transition temperature T_g^a = 230° C, while the remaining base glass displays a second glass transition temperature T_g^b that systematically increases as its Se content is depleted. The present thermal results are in harmony with Raman scattering, neutron diffraction, dielectric spectroscopy and optical microscopy measurements and suggest that Se-rich glasses in the Ag–Ge–Se ternary system intrinsically phase separate on a macroscopic scale.