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 diffrac tion. A significant influence of the flow rate of the quenching gas on the phase composition (the tetragonal to monoclinic ratio varied betw een 0.6 and 3.5) and on the micro-structure was observed, while struct ural parameters of both phases of all investigated samples remained es sentially 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 meas urable change in the crystallite sizes by heating at 845 degrees C. A very high background on the neutron powder patterns may have been caus ed by the presence of pores in the samples.