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Transparent Eu3+-Doped Ferroelectric Bismuth Titanate Glass-Ceramic Nanocomposites: Fabrication and Properties

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Authors to whom correspondence should be addressed. e-mails: basudebk@cgcri.res.in and atiariitk@gmail.com

Abstract

Bismuth titanate (Bi4Ti3O12) (BiT), glass is prepared by the melt-quench technique in the SiO2K2OBi2O3TiO2 (SKBT) system doping with Eu2O3 and transparent BiT glass-ceramics (GC) is derived from it by controlled heat-treatment at 500°C by varying duration. The structural properties of the heat-treated GC are investigated using X-ray diffraction (XRD), electron microscopy [Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM)], and fourier transform infrared reflectance spectroscopy. FE-SEM and TEM images show the formation of polycrystalline spherical particles of 100–200 nm with 10–15 nm crystallites after heat-treatment. A significant increase in εr value (from 20 to 35) was observed with increase in heat-treatment time. The transmission losses of GC which happened with heat-treatment time are due to Rayleigh scattering exhibited by nanocrystallites of BiT. The excitation spectra have been recorded by monitoring emission at 612 nm corresponding to the 5D0 → 7F2 transition and an intense 467 nm excitation band corresponding to the 7F0 → 5D2 has been observed. Emission spectra were recorded by exciting the glass samples at 467 nm. It is observed that with increase in heat-treatment time, the intensity of red emission at 612 nm increases by 8-fold, which has happened due to the occupancy of Eu3+ ions in the low phonon energy crystal sites of BiT.

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