Synthesis and characterisation of dual-phase Y-TZP and RuO2 nanopowders: dense electrode precursors.

The synthesis and characterisation of nanopowders in the dual-phase system tetragonal-Y2O3-doped ZrO2 (Y-TZP) and RuO2 are described. Five powders were prepared from a co-precipitation (CP) method with stoichiometric variation in the RuO2 content (5–46 mol%) and two powders were prepared from solid-phase mechanical mixing of the above oxides prepared separately. In the CP method, an aqueous chlorometal solution containing appropriate precursor ions was co-precipitated in a concentrated aqueous ammonia (pH y14) solution. Following filtration, washing and drying (100 uC), the CP synthesis route yielded black coloured amorphous powders. Crystalline dual-phase powders were obtained after calcination in stagnant air at 600 uC for 2 h. The average Y-TZP and RuO2 crystallite sizes were, respectively, 10 and 20 nm, i.e. a nano/nano powder. The powders were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), backscatter Raman spectroscopy (ZrO2 phase determination) and quantitative X-ray fluorescence (XRF). Time-dependent calcination experiments for samples of similar composition revealed that under the synthesis conditions employed, a composite was formed where a fraction of the crystalline RuO2 phase was initially dissolved in the ZrO2 phase and which gradually transforms to a more stable, distinctly dual-phase system upon prolonged (¢20 h) calcination at 600 uC.