Effect of sintering environment on the structure of calcia-stabilised TiO2-added zirconia solid solutions

Four sets of calcium-stabilised TiO2-added zirconia polycrystals were produced to study the response of zirconia structure to the sintering environment. Two sample sets originated from pressureless sintering of the zirconia powders in air and argon, respectively. In the third set, the zirconia powders were hot-pressed in argon in the unavoidable contact with the graphite foil. The set forth differed from the third one in the presence of WC particulates. Rietveld refinements with X-ray diffraction data were used to determine the phase composition of the sintered bodies and unit cell volumes of zirconia polymorphs. It was found that deoxidation of the calcia-stabilised zirconia solid solutions at 1200-1350 °C is a weak factor for the tetragonal phase content increase. The TiO2 incorporation inhibited deoxidation and decreased the amount of tetragonal polymorph. The importance of additional oxygen vacancies and residual stresses for the stabilisation of tetragonal zirconia was discussed.