Synthesis and characterization of nanocrystalline RuO2-ZrO2

The nanocrystalline samples of zirconium oxide doped with ruthenium oxide ( RuO2) have been synthesized from chlorides as precursors by chemical precip itation method. The as-prepared and annealed powder samples were studied by XRD, TEM and Impedance Spectroscopy, With 7.5 mol% of RuO2, only a small p ercentage of ZrO2 stabilizes in tetragonal form without stabilization in cu bic form. With 9 mol% and above, ZrO2 stabilizes in mixed phases having bot h tetragonal and cubic structure. On annealing, up to 1273 K the proportion of the cubic phase increases; however annealing at temperatures above 1273 K makes the sample to become monoclinic. Average grain size, as determined by Scherrer's formula using X-ray linewidth, increases with increase of an nealing temperature. The same trend is observed in TEM studies. TEM studies show the agglomeration of grains. X-ray diffraction for various concentrat ions of RuO2 shows the presence of small amount of RuO2 as impurity. This i mplies that Ru4+ goes to the interstitial position also in addition to its occupation of substitutional position of Zr4+ due to its smaller ionic radi us (0.062 nm) compared to that of Zr4+ (0.084 nm). The impedance spectrosco py measurement shows that the conductivity decreases with an increase of.-r ain size. The phase changes in the stabilization process with different con centrations and annealing temperatures, and growth of grain size in RuO2 st abilized ZrO2 will be presented. One of the salient points in this study is stabilization of ZrO2 with RuO2 alone without Y2O3 as reported in the lite rature.