Field response of strains in Dielectric BaTiO3 Nanoparticles

We propose to image the domains of cubic Barium Titanate (BTO) nanoparticles in the presence of electric fields up to several MV/m, using Bragg Coherent Diffraction Imaging (BCDI). We will construct thin-layer capacitors, assembled onto lithographic electrode arrays. The cubic phase of BTO above TC = 373K is paraelectric and would not respond to the applied electric field. Below TC, BTO becomes tetragonal and ferroelectric, so can be polarized and store energy. However, when synthesized under hydrothermal conditions, BTO nanoparticles are found to be cubic at room temperature. These particles are found to have a several-fold enhanced dielectric constant, exceeding 6000. Our model is that nano-BTO is cubic on average because of strain, while its 50nm-sized domains are locally tetragonal. We expect to see changes of the domain structure when the capacitor voltage is changed. This will be visible directly in the diffraction patterns, and later revealed by BCDI phase retrieval.