Structural and dielectric properties of laser ablated BaTiO3 films deposited over electrophoretically dispersed CoFe2O4 grains

Abstract

Thin film nanocomposites with mixed connectivity, composed by CoFe2O4 grains, deposited by electrophoresis on Si|Pt substrates, and subsequently covered by a laser ablation deposited BaTiO3 layer were prepared with different cobalt ferrite concentrations. Their structure presented a combination of BaTiO3, with its tetragonal and the orthorhombic phases coexisting at room temperature, and CoFe2O4 with the cubic spinel structure. The cobalt ferrite nanograins were under in-plane tensile stress, while the BaTiO3 phase was under in-plane compressive stress. The dielectric measurements showed that as the barium titanate grain size decreased, its ferroelectric Curie temperature shifted to lower temperatures relative to the bulk. This grain size dependent TC shift was associated and modeled by a core-shell structure of BaTiO3 grains in the films, with a tetragonal core and cubic shell. Additionally, a diffuse tetragonal-orthorhombic phase transition was observed and, in agreement with Raman spectroscopy results, associated to the coexistence of barium titanate orthorhombic and tetragonal phases in the room temperature region. This led to the formation of polar nanoclusters with random polarization orientations, which induced a frustrated phase transition between the tetragonal and orthorhombic phases of barium titanate in the films.

Comparison of Physical/Chemical Properties of Prussian Blue Thin Films Prepared by Different Pulse and DC Electrodeposition Methods

“…As such, the XRD structural results indicate that the films present mainly the insoluble phase of PB. The grain sizes (L) were estimated from the FWHM of the (110) peak using the Scherrer equation, Equation (1) [52][53][54]:…”

Simulation of the temperature profile of BaCaZrTiO3 thin films during laser annealing

“…Multiferroic piezoelectric-magnetostrictive composites have been attracting much attention, since they allow exploring coupled electric/magnetic responses [1,2]. Composite nanostructures made of Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCZT, ferroelectric) thin films on Metglas 2826MB (ferromagnetic) substrates are one of such composites, combining the high piezoelectricity of the BCZT with the high magnetostriction of the metglas, originating a multiferroic material with potential enhanced coupled responses.…”

“…Composite nanostructures made of Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCZT, ferroelectric) thin films on Metglas 2826MB (ferromagnetic) substrates are one of such composites, combining the high piezoelectricity of the BCZT with the high magnetostriction of the metglas, originating a multiferroic material with potential enhanced coupled responses. However, when producing the thin film, high deposition temperatures may be required [2] that modify the substrate properties. In such cases a possible approach is to perform the deposition at low temperatures followed by an annealing process using a laser with a low fluence (laser annealing), which will remove defects that may have accumulated during the deposition, promote the film crystallization and avoid heating the substrate [3].…”