Glasses under study were prepared by a standard press quenching technique. Differential thermal analysis (DTA) measurements have shown that the as-obtained glasses are stable up to 530°C. The DTA traces contain three thermal events: a baseline shift due to the glass transition followed by two distinct exothermic peaks related to crystallization processes. The positions of maxima of those peaks obey a Kissinger formula with the activation energy values: 3.7±0.1eV, 4.3±0.2eV, respectively. Heating of the samples to about 620°C leads to their nanocrystallization. The average grain size in nanocrystalline samples as estimated from scanning electron microscopy (SEM) and X-ray diffraction (XRD) is between 60 and 70nm. The nanocrystallized samples have two important advantages: they are stable to at least 660°C and their electronic conductivity at room temperature is substantially higher than that of the as-prepared glasses (1.2·10 −7 S/cm vs. 1.5·10 −8 S/cm).