Effects of the lapped surface layers on the dielectric properties of ferroelectric ceramics

The effects of lapped surface layers on the dielectric properties of Ba- and Sr-modified lead titanate and lead zirconate ferroelectric ceramics are examined. Specimens with lapped surfaces show anomalous dielectric behaviors, namely, smaller dielectric constant, higher Curie temperature, smaller dielectric loss (below Curie point), and smaller remanent polarization than those of specimens whose surface layers are removed by chemical etching. This may be ascribed to the existence of a lapped surface layer, which seems to be a (0.1–2)-μm-thick nonferroelectric layer of small dielectric constant with a two-dimensional tensile stress of 5–15 kbars. The thinness of the layer results in a large capacitance on the order of 0.5 μF/cm2. The above model for lapped surface layer, especially involving the two-dimensional tensile stress, explains well the anomalous dielectric behaviors measured in this paper.