SINTERING OF ZIRCONIUM TUNGSTATE

摘要

The sintering of a commercial zirconium tungstate powder was investigated to establish suitable processing conditions for obtaining dense materials. A minimum heating or cooling rate of about 600℃/h is needed to avoid decomposition of the material below 1105℃. Above 1200℃, densificalion occurs easily and there is almost no influence of particle size on densification: even relatively coarse powders densify readily. However, large pores develop in the material by decomposition and evaporation of WO_3. Milling the powder in an effort to reduce the sintering temperature caused the powder to become amorphous. This allowed densification to proceed at lower temperature but gave rise to cracking as the crystalline structure reformed. As an alternative, reaction sintering of zirconium oxide and tungsten oxide powders was also explored. It was found that this route allows high relative density without cracking to be obtained at a sintering temperature sufficiently low to avoid the formation of large pores due to decomposition. Full conversion was only obtained by reaction at 1200℃. leading to pore formation.