Lattice Image Observations of Nanoscale Ordered Regions in Pb(Mg 1/3 Nb 2/3 )O 3

The grain-size dependence of nanoscale ordered regions in Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) has been studied using lattice images obtained by transmission electron microscopy. It was found that the size of nanoscale ordered regions, which is strongly related to dielectric properties, depends on the grain size. The nanoscale ordered regions of fine-grained PMN with average grain sizes of 0.32 and 0.15 µ m are clearly smaller than those of coarse-grained PMN with an average grain size of 1.95 µ m. The dielectric constant is found to be markedly low with grain size below ∼0.3 µ m.