POWDER DIFFRACTION INVESTIGATIONS OF PLASMA-SPRAYED ZIRCONIA

The crystallographic and microstructural parameters of plasma sprayed pure zirconia powders were studied by X-ray and neutron powder diffraction. A significant influence of the flow rate of the quenching gas on the phase composition (the tetragonal to monoclinic ratio varied between 0.6 and 3.5) and on the micro-structure was observed, while structural parameters of both phases of all investigated samples remained essentially unchanged and were close to those reported in the literature. These results do not support the concept of a critical particle size effect as a stabilizing factor for the tetragonal phase. A transition from a tetragonal to a monoclinic phase was observed without any measurable change in the crystallite sizes by heating at 845 degrees C. A very high background on the neutron powder patterns may have been caused by the presence of pores in the samples.