Bismuth Oxide Influencing Tungsten Trioxide Ceramic Property

When the doping concentration is 0.2mol% and the sintering temperature is about 1100 ℃, the density of the WO₃ ceramics doped Bi₂O₃ can reach 91%. When the doping concentration is 0.2mol% , WO₃ ceramics densification will decline; the sintering temperature is lower than 1100 ℃, the density increases gradually, but when the sintering temperature is 1100 or higher than 1100 ℃, the density of the ceramic will decline ; the best sintering time is 2h, extend the time will make the ceramics sintered density decreases. After analysis, the major causes for this phenomenon are: WO₃ melting point is 1273 ℃, Bi₂O₃ melting point is 860 ℃, the formation of the sublimation are the two substances .

Comparing with non-doped WO₃ ceramics, WO₃ ceramics doped Bi₂O₃ varistor voltage declines rapidly, this shows the rapid growth of the ceramic grains causing breakdown voltage drop. When the sintering temperature of WO₃ doped Bi₂O₃ ceramics is 900 ℃, WO₃ ceramics do not have pressure-sensitive properties, when the temperature is 900 ℃ ~ 1100 ℃, the pressure-sensitive is maximum coefficient, when the sintering temperature is 1100 ℃, the pressure-sensitive decreases with the temperature rises, it disappears after sintering temperature is higher than 1100 ℃. When Bi₂O₃ doping concentration is 0.5mol%, the sintering time is 2h.

Doping Bi₂O₃ having a significant effect on the microstructure of WO₃ ceramics; doping can play a role to help promote sintering ceramics; doping can improve the characteristics of the ceramic varistor.