CHARACTERIZATION OF YTTRIA-DOPED ZIRCONIA POWDERS PRODUCED BY PLASMA-CHEMICAL METHOD

Ultrafine non-doped and yttria-doped zirconia (ZY) powders have been p roduced by a single-step plasma synthesis method. The amount of yttria doping was varied between 0 and about 10 mol%. The phase composition, structural parameters and morphology of the as-prepared powders have been examined by X-ray diffraction, neutron diffraction and electron m icroscopy. The average particle size of the produced powders was found to be around 30 nm, changing little with composition. The particles w ere mostly spherical but a large number of faceted single crystals wer e also present, as revealed by high resolution transmission electron m icroscopy. The ZY ultrafine powders were mixtures of a cubic and a non -transformable tetragonal zirconia phases. The amount of the tetragona l phase decreased with the overall yttria content but with a compositi on that remained almost the same. Neutron diffraction revealed diffuse scattering located at the positions of tetragonal maxima forbidden fo r cubic structure. The origin of diffuse scattering is associated with oxygen vacancies, either due to relaxation around Y3+ ions or due to ordering of vacancies. X-ray diffraction showed no diffuse scattering.