**14. Sintering in vacuum**

While annealing Zr2O in air at 13000C was accompanied with pronounced phase changes, phase composition remained unchanged even with prolonged holding at 13000C in vacuum. Vacuum sintering of powders with complex morphology at a high temperature thus allowed obtaining a dense ceramic based on Zr2O3 and Y2O3 with no monoclinic phase, despite the strong recrystallization of grains of the tetragonal phase.
