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Sm-doped BaTiO₃ thin films with ~200 nm thickness fabricated by rf magnetron sputtering system onto Pt/Ti/SiO₂/Si substrates have been investigated. The effects of postannealing and the dopant content in a range of 0.1 to 2.2 at.% on microstructure and electrical properties were studied. The films were found to be amorphous in the as-deposited state and became fully crystallized after annealing at 750°C and above. The addition of Sm in the BaTiO₃ films resulted in the inhibition of grain growth. Electrical characterizations show that the dielectric permittivity increased with increasing annealing temperatures and the 2.2% Sm-doped film had the low leakage current of 1.29×10^-9 A at an applied electric field of 100 KV/cm.

The phase formation and thermal-induced phase transformation are studied in BaTiO₃ nanoparticles. 2 h of heating a polymer precursor at 550°C in air formed a single phase BaTiO₃ of 15 nm average crystallite size D. The X-ray diffraction peaks are analyzed assuming a P_nma orthorhombic (o) crystal structure of lattice parameters a = 0.6435 nm, b = 0.5306 nm, and c = 0.8854 nm. The lattice volume V = 0.3023 nm³, with z = 4 formula units, yields a density ρ = 5.124 g/cm³. This is a new polymorph in comparison to well-known P_m3m tetragonal (t) structure, V = 0.0644 nm³ or ρ = 6.016 g/cm³ (z = 1). An o ↦ t transformation appears on heating at temperature as high as 650°C in air. A proposed model explains the transformation above a certain D value in terms of the Gibbs free energy. Unless heating above 750°C, the two phases coexist in a composite structure (D≤27 nm), with as much residual o-phase trace as ~28 vol%. As a function of temperature both the phases decrease in the V values up to 0.2975 and 0.0643 nm³ at 750°C respectively (0.0650 nm³ at 650°C). This is an important parameter for designing useful ferroelectric and other properties in a hybrid composite structure.

The spin Hamiltonian parameters and local structure for the tetragonal Rh²⁺ center in rhombohedral BaTiO₃ are theoretically studied from the perturbation formulas of these parameters for a 4d⁷ ion with low spin (S=1/2) in tetragonally elongated octahedra. This center is ascribed to substitutional Rh²⁺ at the Ti⁴⁺ site in BaTiO₃. The [RhO₆]^10- cluster suffers relative elongation (characterized by the elongation parameter ρ ≈ 0.9%) along the [100] axis due to the Jahn–Teller effect. The tetragonal elongation can entirely depress the slight trigonal distortion of the original Ti⁴⁺ site in rhombohedral BaTiO₃. The calculated spin Hamiltonian parameters based on the above Jahn–Teller elongation show good agreement with the experimental results.

The reaction conditions of size-controlled BaTiO₃ nanopowder prepared by microwave irradiation have been investigated. It has found that the dosage of alkali, reactant concentration and reaction time are very important factors that affect average grain size of BaTiO₃ powder. Through these investigations, we synthesized adulterated BaTiO₃ nanopowder from an aqueous solution of barium hydrate and titanium tetrachloride, and use microwave irradiation as a heating source. XRD of the series of the nanometer powder demonstrates that pure and adulterated BaTiO₃ of cubic system has been prepared. Through TEM we found the products have a shape of uniform, substantially spherical particles with an average grain size to be 70 nm.