Glass-ceramic-metal nanocomposites containing a ferroelectric phase

Abstract

Ferroelectric crystallites of dimensions-few microns were grown within suitably chosen glass compositions. The glasses were prepared by both melt-quenching and solgel techniques. Typical phases were BaTiO₃, Pb(Zr_0.5 Ti_0.5) and LiNbO₃ respectively. Nanoparticles of silver or nickel were synthesized by subjecting the ion exchanged glass-ceramics to a reduction treatment. The dielectric permittivities of the nanocomposites were found to be much higher than those of the glass-ceramic specimens. Space-charge model failed to explain this enhancement. A quantum mechanical model was used to explain this effect. Silver nanowires of diameter ~5 nm were grown in glass-ceramics containing LiNbO₃ crystallites by an electrodeposition technique-the voltage applied being 20 volts. The wires were aligned parallel to the applied field. This is ascribed to the internal field increase due to the presence of ferroelectric crystals. By applying a suitable voltage pulse, break junctions were induced in these wires. Voltage-Current characteristics of the resultant structure showed the field emission effect with a high field enhancement factor.