ORIGIN OF F SPOTS AND STRESS SENSITIVITY IN LANTHANUM LEAD-ZIRCONATE-TITANATE

In this study a systematic microstructural characterization of La-modi fied lead zirconate titanate was carried out by hot- and cold-stage tr ansmission electron microscopy and selected area electron diffraction. The existence of 1/2[111] superlattice reflections (F spots) became e vident near 300-degrees-C on cooling. The intensity of the F spots was found to increase with decreasing temperature, approaching a near con stant intensity below 100-degrees-C. In conjunction with compositional studies, it was proposed that the F spots arise from a doubling of th e unit cell associated with a tilting of oxygen octahedra. The presenc e of F spots at temperatures approaching the onset of local polarizati on was then interpreted as the existence of a hierarchy-of domain stat es. This hierarchy was proposed to consist of an average-cubic macrosc opic structure containing rhombohedral micropolar regions on the scale of 50-100 angstrom that contain ferroelastic microtwins on the scale of several tens of angstroms.