High Yield Hydrothermal Synthesis of Nano‐Scale Zirconia and YTZP

Many techniques exist to synthesize zirconia and YTZP with a nano‐scale particle size, but a recently developed hydrothermal precipitation procedure has shown promise in producing high‐yield quantities of well‐dispersed 8–10 nm zirconia and YTZP . Using bicine as a complexing agent, a homogeneous solution of zirconyl nitrate and yttrium nitrate is formed; after hydrothermal treatment, 8–10 nm tetragonal zirconia or YTZP particles are precipitated. With the modified hydrothermal procedure, powder yield was increased to 100 g of powder per liter of reactant solution without significantly changing the powder characteristics. X ‐ray diffraction and R aman spectroscopy were used to verify that the tetragonal phase was formed in the 1 YTZP composition. Complementary particle size measurements were made using dynamic light scattering, BET nitrogen adsorption, and X ‐ray diffraction; differences in measured particle size are discussed, and all three techniques verify the 8–10 nm particle diameter. Particle morphology and impurity content were measured with transmission electron spectroscopy and X ‐ray fluorescence, respectively. To overcome the increased likelihood of agglomeration that accompanies the increased synthesis, wash solutions of deionized water, bicine, and oxalic acid were compared, and the particle–particle interactions of nano‐ YTZP in these wash solutions and in ethanol are modeled with modified DLVO theory. The results show that yttria leaching is prevented and dispersion is promoted by laundering with a solution of oxalic acid and dispersing into deionized water, both adjusted to a pH value of 9.