Functionalization of BaTiO₃ nanoparticles with electron insulating and conducting organophosphazene-based hybrid materials

Abstract

Novel core-shell structured organophosphazene (OPZ) coated BaTiO 3 nanoparticles (OPZ@BaTiO 3 ) were produced via a facile and rapid one-step nucleophilic substitution reaction in ambient conditions. The morphology, structure and textural properties of the core-shell nanoparticles were analysed via electron microscopy, spectroscopy, thermogravimetry and porosimetry, and the dielectric properties were evaluated by impedance spectroscopy. The thickness of the cross-linked OPZ shell was readily tailored by varying the weight ratio of the OPZ monomers to BaTiO 3 , which in turn affected the relative permittivity and the frequency dependence of the OPZ/BaTiO 3 particles. A subsequent carbonisation treatment of the OPZ@BaTiO 3 at 700 C transformed the polymeric OPZ shell to a microporous carbonaceous shell, which dramatically increased the electrical conductivity of the particles.Organophosphazene chemistry offers a facile route to functionalise BaTiO 3 nanoparticles without any pre-treatment, and generate a range of core-shell BaTiO 3 nanoparticles with tailored dielectric and electrically conductive properties that can be used as active fillers for polymer based nanocomposites and energy storage applications. The effectiveness and advantages of OPZ chemistry over other reported methods in forming core-shell particles are demonstrated. Fig. 2 SEM images of (a) the commercial BaTiO 3 particles after sonication, (b) OPZ@BaTiO 3 -0.25, (c) OPZ@BaTiO 3 -0.5, (d) OPZ@BaTiO 3 -1, (e) OPZ@BaTiO 3 -4. Scale bar at 500 nm. (f) Representative spectra from EDX elemental analysis. This journal isFig. 7 (a) AC conductivity of the OPZ@BaTiO 3 and C@BTO samples and comparison with the dense OPZ, (b) phase angle of OPZ@BaTiO 3 and C@BTO samples. Phase angle approaching 0 deg indicates conductive behavior, approaching 90 deg indicates capacitative behavior, (c) relative permittivity of the OPZ@BaTiO 3 samples and comparison with the dense OPZ nanospheres. (d) Dielectric loss of the OPZ@BaTiO 3 samples and comparison with the dense OPZ nanospheres.This journal is