Observation of a sequence of domain-like states with increasing disorder in ferroelectrics

Transmission electron microscopy studies of the (1 - x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) (PMN-PT (1 - x)/x) and the (Pb1-yLay)(Zr0.65Ti0.35)O-3 (PLZT y/65/35) crystalline solutions have been performed for x = 0.1, 0.2, 0.35 and 0.60 and y = 0.00, 0.05, 0.07 and 0.10. Bright-field imaging has revealed a common sequence of domain-like states with either increasing x or decreasing y. Normal micron-sized ferroelectric domains were found for x > 0.40 or y < 0.05. However, the presence of internal subdomain structures was found within the micron-sized domains, indicating polarization non-uniformities. Tweed-like structures were found for x approximate to 0.35 or y approximate to 0.07. These tweed-like structures are similar to those previously reported in pre-martensitic states. Paraelectric clusters were found for x < 0.30 or y > 0.08. The paraelectric cluster state was characterized by the lack of self-assembly amongst clusters and the presence of relaxer behaviour in the macroscopic response characteristics. The composition PMN-PT 65/35 was then modified with La for a detailed study of the transition between the tweed-like precursor and paraelectric cluster states with increasing impurity content.