Evidence of nearest-neighbor ordering in wet-processed zirconia-nickel composites

Monolithic zirconia-nickel (ZrO2/Ni) cermets have been prepared by a wet-pr ocessing method with nickel volume concentrations of 16%-40%. Microstructur al analysis performed on scanning electron microscopy images has revealed e vidence of a partial ordering of metallic particles inside the ceramic matr ix. This ordering does not appear in mullite/molybdenum cermets. Complex im pedance measurements have shown that the percolation threshold of ZrO2/Ni c ermets appears at a filling factor (f(c)) of 0.34, exceeding the theoretica l value (f(c) = 0.16), as a consequence of its microstructural order. Elect rical measurements display the expected increase of capacity near the perco lation threshold. These results open the possibility to design new devices with the appealing electric, magnetic, and mechanical properties that are p redicted by the percolation theory.