An investigation of the effects of small additions of Fe,O, to lead zirconate-lead titanate ceramics with compositions between 45 and 60 mol% lead zirconate has shown that, with 2 moles of PbO to balance each mole of Fe203, the solubility of Fe,Bn was about 0.8 wt% in compositions near the tetragonal-rhombohedra1 boundary. The dielectric constant and dissipation factor for both rhombohedra1 and tetragonal materials were decreased by addition of iron oxide, whereas the mechanical quality factor and frequency constant were increased. The dependence of the electromechanical properties on grain size was qualitatively similar for both undoped and iron oxide-doped materials; the presence of iron oxide inhibited grain growth and lowered the limiting grain size below which the electromechanical properties change rapidly with grain size.

Lead zirconate-lead titanate ceramics, covering the compositional range 40 to 70 mole per cent lead zirconate, were prepared by cold pressing and sintering from co-precipitated powders. For these ceramics the maxima in the values of dielectric constant and electromechanical coupling factor that occur at the rhombohedral-tetragonal boundary were found to be higher and sharper than previously reported for . unmodified lead zirconate-titanate. Dielectric and mechanical losses were lower in the tetragonal than in the rhombohedral phase. Determination of the variations in properties with temperature confirmed the previously reported shift in the phase boundary toward higher zirconate compositions with increasing temperature. It was found that changes in electromechanical properties resulting from loss of lead oxide could be explained on the basis of the formation of a more titanaterich solid solution, accompanied by the precipitation of zirconia

Lead zirconate-titanate piezoelectric ceramic disks were prepared from spray-dried, co-precipitated powders by cold-pressing and sintering. The effects of several processing variables on the electromechanical properties of the ceramics were determined. It was found that satisfactory samples could be fabricated from the spray-dried powders without milling, and that the forming pressure could be varied over a considerable range with little effect on the final properties. Disks sintered in oxygen showed only a slight improvement in properties over those sintered in air. In general, an increase in planar coupling factor could be achieved by increasing the sintering temperature or sintering time, but some decrease in dielectric constant was observed at the highest temperatures and longest times. Precipitates with a slight excess or deficiency of lead oxide tended toward stoichiometry with respect to lead oxide during sintering under appropriate conditions.