Adsorption of Polyvinylpyrrolidone (PVP) and Its Effect on the Consolidation of Suspensions of Nanocrystalline CeO₂ Particles

CeO2 particles with an average size of ∼9 nm were synthesized under hydrothermal conditions. The adsorption of polyvinylpyrrolidone (PVP) on to the particle surfaces was measured in aqueous suspensions in the pH range of ∼3.7 to 11.5. The amount of adsorbed PVP decreased significantly with increasing pH value. For suspensions prepared at a pH value of ∼3.7, complete adsorption occurred for ∼2.5 wt % of PVP added to the suspension. Further additions of PVP produced a gradual increase in the adsorption until a limiting value was reached when the total amount of PVP added to the suspension was 10 wt %. At this PVP concentration, ∼6 wt % of the PVP was adsorbed and ∼4 wt % remained free in solution. The effect of the adsorbed PVP on the microstructural homogeneity of films deposited by spin coating of suspensions was investigated. With no addition of PVP, crack-like voids were prevalent in the dried and sintered films. Crack-free films were obtained from suspensions containing 10 wt % of PVP. Higher PVP additions (25 wt %) produced an increase in the viscosity of the suspension but no observable change in the microstructural homogeneity of the films. The use of adsorbed polymers for steric stabilization coupled with data from the adsorption isotherms is shown to provide a rational approach to the deposition of homogeneous films from suspensions of nanocrystalline particles