Structure and electron charge-density analysis of nano-sized BaTiO3 powder prepared by solvothermal method

The BaTiO3 powder with the average particle size of 20 nm were synthesized by a solvothermal method using Ba and Ti alkoxide solutions as precursors. The structural parameters of BaTiO3 powder were successfully determined by the Rietveld refinement based on the analysis of Raman spectra. The final weighted R-factor, Rwp, was 9.12% and the goodness-of-fit indicator, S (=Rwp/Re), was 1.28. The BaTiO3 powder consisted of cubic and tetragonal phases at room temperature. The weight fraction of cubic and tetragonal phases based on the refined scale factors was 83.2% and 16.8%, respectively. The lattice parameters for cubic and tetragonal phases were a (=b = c) = 4.0114(3) Å, and a (=b) = 3.9954(2) Å and c = 4.0327(2) Å, respectively. According to the analysis of the electron charge-density distributions by maximum entropy method based on the observed structural factors to understand the chemical bonding nature of BaTiO3 powder, the ferroelectric phase was stabilized by ionic and weak covalent bonding.