Grain size and domain size relations in bulk ceramic ferroelectric materials

A study of the ferroelastic domain size variations with grain sizes in Pb(Zr,Ti)O₃[PZT] ferroelectric ceramic has been conducted. Experimental results determined by a transmission electron microscopy (TEM) study on hard and soft PZT ceramics indicate that it is possible to observe a bulk metastable domain configuration in a thinned foil. The transmission electron microscopy observations demonstrate that the domain structures formed at the paraelectric-ferroelectric phase transition are strongly dependent on the elastic boundary conditions and crystallite sizes. Statistical analysis of the domain size distributions in PZT reveals that the traditional parabolic relation between grain size and domain size is only good for a limited size range of 1-10 μm. For grains size > 10 μm, the exponent tends to be smaller than 1/2, while for grain size < 1 μm the exponent is larger than 1/2. We also report the analysis on poled ceramics which reveals for the first time direct evidence for transgranular domain switching mechanisms.