Gold‐Nanoparticle‐ and Gold‐Nanoshell‐Induced Polymorphism in Poly(vinylidene fluoride)

PVDF nanocomposites are prepared through solution mixing of Au‐NPs or Au‐NSs with PVDF. The novel optical properties of Au‐NPs and ‐NSs are retained as confirmed from UV‐Vis spectra. Analysis of resulting nanocomposites by FT‐IR, XRD, and DSC shows an obvious polymorphism change from α‐ to β‐form compared to PVDF prepared under the same conditions. The β‐polymorph seems to be more prominent with higher concentration of Au‐NPs (0.5%) and even more so with Au‐NSs. Thermogravimetric analysis shows that both nanocomposites have better resistance toward thermal degradation. Combination of novel optical properties of Au‐NPs or Au‐NSs with induced ferroelectric‐active β‐polymorph in PVDF can lead to new design of optical, piezoelectric devices.

     

Density functional theory investigation of site predilection of Fe substitution in barium titanate

The site predilection and effects of the impurity in the form of Fe (II) and Fe (III) in the tetragonal barium titanate lattice were systematically determined by density function theory calculations. All electron calculation was carried out in the local density approximation (LDA). It is shown that both Fe (II) and Fe (III) prefer to substitute at the titanium site with oxygen vacancy compensation as a result of lowest substitution energy. Effect of Fe dopant both in form of Fe (II) and Fe (III) at titanium site with oxygen vacancy compensation lead to change in electrical property in terms of energy band structure of the tetragonal barium titanate lattice.