Seven Sc 2 O 3 , Y 2 O 3 -stabilized ZrO 2 (SYSZ) powders having 7 wt.% stabilizer, which was varied from 0%-100% Sc 2 O 3 , were prepared by a sol-gel process and tested for resistance to destabilization by molten NaVO 3 at 700°C and 900°C. The Y 2 O 3 -rich SYSZ powders were destabilized by chemical reaction with the NaVO 3 , with YVO 4 being produced, while the Sc 2 O 3 -rich powders were destabilized by a mineralization effect (no chemical reaction) by the molten NaVO 3 . Aging at 1400°C for 140 hrs substantially improved the vanadate resistance of the Sc 2 O 3 -rich, but not the Y 2 O 3 -rich, SYSZ powders. The SYSZ powders stabilized by Sc 2 O 3 plus 10%-20% Y 2 O 3 , after 1400°C aging, showed 5-10 times better resistance to vanadate-induced destabiliziltion than the 100% Y 2 O 3 -stabilized SYSZ powder. In addition, the Sc 2 O 3 -(10-20%)Y 2 O 3 powders gave less monoclinic formation, and therefore evidenced better high temperature phase stability, than the 100% Y 2 O 3 -stabilized powder during the 140 h of 1400°C aging.