Conductivity stabilization by metal and oxide additives in ceramics on the basis of VO2 and glass V2O5–P2O5

Conductivity behavior during the temperature cycling through the phase transition temperature of VO2 (Tt = 68 °C) was investigated in glass-ceramics based on VO2 and vanadium phosphate glass (VPG) for compositions without and with Cu and SnO2 additives. Copper and SnO2 additives stabilize the conductivity of glass-ceramics at temperature cycling. For ceramics (wt%) (80 − y)VO2–5Cu–15VPG–ySnO2 the best stabilizing effect takes place when SnO2 content is in the interval 35 wt% < y < 50 wt%. Ceramics with such SnO2 content keeps a stable value of the conductivity change (∼102) in the vicinity of VO2 phase transition temperature and shows the conductivity decrease no more than of 2.5 times after 3000 thermal cycles. The reasons of conductivity stabilizing in VO2-based glass-ceramics with additives of Cu and SnO2 are being discussed. The analysis resting on the percolation theory has shown the increase of conductivity stability in VO2-based glass-ceramics when the VO2 volume fraction and the average size of VO2 crystallites decrease and the ceramics surface tension increases.