The effect on zirconyl type salt on the phase composition, particle size and sinterability of zirconia based powders obtained via reversed co-precipitation

Stabilized zirconia is a structural ceramics being of high interest due to large area of applications in industry. Zirconia ceramics is widely used in the fields of hydrogen energy, high temperature oxygen sensing, biomedical applications due to the unique combination of high oxygen-ion conductivity, strength, fracture toughness, and low thermal conductivity. Despite the variety of techniques is available for zirconia powders manufacturing, there is a need for nanosized powders with the controlled particle size distribution and high sinterability. The work aims the study of the nature of the zirconyl salt (nitrate and chloride) on the phase composition, particle size, and crystallization temperatures and enthalpies of the zirconia powders produced via sol-gel synthesis in a variation of the co-precipitation. The undoped zirconia, 4 and 8 mol.% yttria stabilized zirconia (4YSZ and 8YSZ) were studied. Special attention is paid to the differences in the hydrolysis and precipitation behavior taking place during sol-gel synthesis from zirconyl nitrate and chloride salts. The annealing of 4YSZ powder performed in the range 650-1100 degrees C for 3 h showed the stability of the tetragonal phase. The powders manufactured via the sol-gel method demonstrated excellent sinterability during spark plasma sintering (SPS) compared to the SPS-ed commercial zirconia powders. Undoped zirconia ceramics SPS-ed at 1450 degrees C for 1 h showed relative density over 99% and Vickers hardness of 730 +/- 80 HV0.3, while the ceramics SPS-ed from Tosoh powders at the same conditions showed relative density of 98.2% and Vickers hardness of 280 +/- 6 HV0.3.