Nanoscale BaTiO3​ particles (~10 nm) prepared by ball-milling a mixture of
oleic acid and heptane have been reported to have an electric polarization
several times larger than that for bulk BaTiO3​. In this work, detailed
local, intermediate, and long-range structural studies are combined with
spectroscopic measurements to develop a model structure of these materials. The
X-ray spectroscopic measurements reveal large Ti off-centering as the key
factor producing the large spontaneous polarization in the nanoparticles.
Temperature-dependent lattice parameter changes reveal the sharpening of the
structural phase transitions in these BaTiO3​ nanoparticles compared to the
pure nanoparticle systems. Sharp crystalline-type peaks in the barium oleate
Raman spectra suggest that this component in the composite core-shell matrix, a
product of mechanochemical synthesis, stabilizes an enhanced polar structural
phase of the BaTiO3​ core nanoparticles.Comment: 5 figures in main text. 1 table and 3 figures in supplementary
documen