Studies on microstructure and microproperties of PLZT ceramics

The microstructure of PLZT transparent ferroelectric ceramics were studied by high-resolution electron microscopy (HREM) and electron diffraction. The following experimental results were obtained: 1. (1) The structure of micro-domains in the cubic α phase is exactly the same as that of the ferroelectric β phase after poling. The ‘fringe’-shaped micro-regions in the HREM micrograph of 7·9/70/30 PLZT is the result of lattice overlapping of the orthorhombic micro-domains and the cubic α phase matrix. 2. (2) A 2 × d 111 superlattice along the 〈111〉 directiion was observed in 7·9/70/30 PLZT ceramics. It is probably the result of gliding or rotation on the {111} plane due to self-regulation of the structure in the presence of point defects. 3. (3) The lattice image micrographs taken near the grain boundary show that the grain boundaries in PLZT ceramics are very fine. Most of their widths are less than 6Å; some are only 2–3 Å. However, in some places the grain boundaries are broadened, and may reach several tens of ångströms. The structure of broadened grain boundaries appears amorphous. In addition, using specially constructed instruments, the electrical and electrooptical properties of single grains in PLZT ceramics were measured and compared with the properties of the ceramic materials.