Direct observation of polar nanostructures in PLZT ceramics for electrooptic applications

Transparent Pb_1-yLa_y(Zr_1-xTi _x)_1-yO₃ (PLZT, y=0.0975, x=0.35) ceramics prepared via hot pressing techniques were studied via piezoelectric force microscopy (PFM). Clear piezoelectric contrast is observed in a cubic relaxor phase indicating spatial distribution of polarization with an average cluster size of about 50 nm. The irregular polarization pattern is associated with the formation of a glassy state, where random electric and stress Fields are responsible for the disruption of the long-range ferroelectric order. Local poling of the ceramics resulted in the formation of a stable micron-size domain that could be continuously switched under varying dc bias (local hysteresis loop). The applied voltage of 10-12 Volts was enough to switch relaxor into the ferroelectric state. Fractal and correlation analysis of the observed images is presented. The fractal dimension close to 1.55 is consistent with the random distribution of charge defects in this material. The nature of the observed phenomena is discussed based on the current understanding of relaxor state in PLZT and possible effect of PFM instrumentation.