Structural Transitions of Silicate Nanocrystals in the Glass
American Journal of Materials Science
The temperature dependences of resistivity and thermopower measurements reveal that nanocrystals of silicates in lead-silicate glass of various compositions undergo structural transitions in the temperature range of 800 -1000 K. The diameter of these nanocrystals estimated from Scherrer's formula is about 0.8 -1.6 nm and each nanocrystal consists of 8 -64 unit cells. Structure transitions are detected as sharply maxima of resistivity ρ and thermopower S at temperature T = 800 -100 K.
... -100 K. Lead-silicate glass was doped by RuO 2 up to 16 weight% to facilitate the measurements of the ρ and the S. The doped lead-silicate glass has a metal-like behavior at the room temperature: the temperature dependences ρ(T) and S(T) are very slow, the value of the S is typical for metals (few and tens of μV/K). Beyond the maximum of the resistance (temperature T > 1000 K) doped lead-silicate glass turns into typical semiconductor having energy gap about 0.05 -1.5 eV depending on the composition of the glass. Anomalous thermal expansion of the RuO 2 relict crystals is detected at the temperatures of 800 -1000 K as well.