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 degrees 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 +/- 0.1 eV, 4.3 +/- 0.2 eV, respectively. Heating of the samples to about 620 degrees 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 70 nm. The nanocrystallized samples have two important advantages: they are stable to at least 660 degrees 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). (C) 2010 Elsevier B.V. All rights reserved.