Transmission Electron Microscopy Study of Strontium Barium Niobate Relaxors

摘要

Transmission electron microscopy (TEM) investigations have been performed on Sr_xBa_(1-x)Nb_2O_6 (SBN x/1-x). Bright-field imaging of <100>-orientated SBN 60/40 and 75/25 crystals revealed nanopolar domains with a strong shape anisotropy. The morphology of the nanopolar domains was needle-like. Selected area electron diffraction (SAED) patterns revealed the existence of 1/x[110] incommensurate modulations. Dark-field imaging of the incommensurate reflections found the existence of nanometer-sized ferroelastic domains. Diffuse scattering was observed in the SAED patterns along the <100>. This diffuse scattering is believed to arise due to strain gradient interactions between the A-site cation distribution and the incommensuration.