Structure-property relationships in strontium barium niobate I. Needle-like nanopolar domains and the metastably-locked incommensurate structure

Abstract

Transmission electron microscopy investigations have been performed on Sr_xBa_1-xNb₂O₆ (SBN x(1 - x)). Bright-field imaging of ⟨100⟩-oriented 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 nanometre-sized ferroelastic domains. Diffuse scattering was observed in the SAED patterns along the ⟨100⟩ direction. This diffuse scattering is believed to arise due to strain gradient interactions between the A-site cation distribution and the incommensuration.