Optical and dielectric properties of Bi2Ti2O7/Bi4Ti3O12 nanocomposite

Abstract Bismuth titanate pure pyrochlore phase Bi2Ti2O7 (BT2) and its nanocomposite Bi2Ti2O7/Bi4Ti3O12 (BT2/BT4) are synthesized using the coprecipitation method at optimum reaction parameters. XRD results reveal the formation of pyrochlore cubic single phase in BT2 while a mixed-phase consisting of pyrochlore cubic and perovskite Aurivillius orthorhombic phase (Bi4Ti3O12) in BT2/BT4. The nanocomposite sample BT2/BT4 shows the smaller crystallite size (∼30 nm) and larger microstrain than BT2 nanoparticles. The average particle size is calculated using FESEM micrographs are ∼40 nm and ∼60 nm in BT2/BT4 and BT2 samples respectively. The presence of only Bi, Ti and O elements in both samples are confirmed by the EDX spectrum. FTIR spectra of BT2/BT4 confirms the vibrations corresponding to perovskite octahedral in additions to pyrochlore metal oxide vibrations. An optical band gap of nanocomposite BT2/BT4 is much smaller (1.65 eV) than pure phase BT2 sample (2.33 eV). Dielectric analysis reveals high dielectric constant and large a.c. conductivity in BT2/BT4 than the BT2 sample. The tuned optical and dielectric properties of BT2/BT4 nanocomposite shows that this nanocomposite can be further used in photovoltaic applications and as a photocatalyst for solar water splitting or organic waste degradation reactions.