Neutron thermodiffraction study of the crystallization of Ag–Ge–Se glasses: evidence of a new phase

Silver-containing chalcogenide glasses are potential candidates for electrical memory manufacturing. In order to study the glasses under dynamic conditions, using the temperature as the main parameter, a neutron thermodiffraction study of three Agx(Ge0.25Se0.75)100−x glasses (x = 5,15 and 25) was carried out. Two in situ diffraction experiments were performed: a first series including heating ramps from room temperature up to 350 °C and a second one comprising the measurement of an isotherm at about 300 °C for 5 h. For the three studied glasses two stable crystalline phases were formed during the heating process: the cubic Ag8GeSe6 appeared first, followed by the crystallization of monoclinic GeSe2. The crystallization process for the Ag-rich (x = 15 and 25) glasses was more complex, with the appearance of a new unstable phase at high temperature, i.e. Ag2GeSe3. Such a phase decomposed with time or temperature to produce a new phase, Ag10Ge3Se11, along with the stable GeSe2. This phase has never been reported to date while the existence of Ag2GeSe3 was still controversial.