DETERMINATION OF REGION SIZE OF INHOMOGEN EITY IN LEAD TITANATE ZIRCONATE

The compositional homogeneity in the ceramic solid solutions is settle d both by the process of the mixing of raw materials and by that of th e diffusion during the firing. The mechanical mixing of raw materials is not effective against the homogenization below the grindable size. The homogenization process by the diffusion is not effective at large size. The gap where neither mechanical mixing nor diffusion is effecti ve was considered to be the origin of the inhomogeneity in solid solut ions. In order to verify this, a method to evaluate the region size of inhomogeneity was developed. Five areas having a certain size were ra ndomly chosen on the EPMA image of a sample. Each area was divided int o sixteen portions and the standard deviation of composition among the se portions was estimated. This standard deviation can be considered a s a degree of compositional inhomogeneity. The average standard deviat ion among the five areas was calculated. Such calculation was tarried out for various sizes. The average standard deviations were plotted ag ainst the size. Plots for models, in which the distribution of the com position forms a cheek pattern, exhibited peaks. The position of the p eaks corresponded to the size of the check patterns. This method was a pplied to PZT samples prepared by the solid state reaction. The plots revealed the presence of the gap where neither mechanical mixing nor d iffusion is effective.