Dispersion of ZnO Nanocrystals Using Ammonium Polycarboxylate (AMP) for the Fabrication of ZnO-Based Ceramics

The effects of ammonium polycarboxylate (AMP) on the dispersion of zinc oxide nanopowders were investigated in this study. Good dispersibility and stability in ZnO suspension with a dispersant content of 0.5 wt.% at pH 10 was observed by field emission scanning electron microscopy, and was confirmed by sedimentation experiments. The adsorption state of AMP on the surface of nano-sized ZnO powder was examined by Fourier transform infrared spectroscopy. For the ZnO nanopowders with various AMP amounts in the alkaline region, a maximum absolute zeta potential of 55.8 mV was measured at pH 10, which correlated well with the saturation amount of adsorbed AMP. Compacted varistor discs were prepared from the nano-origin ZnO powders before and after AMP absorption, showing sintered densities of 97.6% and 98.4%, respectively. The advantages of AMP were clearly seen in grain structuring, in addition to the enhanced densification and homogeneous microstructures for obtaining a high nonlinear coefficient.