Abstract:
Barium titanate (BaTiO3) nanoparticles synthesized at 200 C by sol- hydrothermal process
demonstrated stabilization of orthorhombic and tetragonal phases. The influence of annealing at different
temperatures (100, 200, 300, 400, 500 & 800 C) on the phase separation/transition is investigated in this
study. The annealing process had substantial impact on the structural and phase variation in BaTiO3
nanopowder as observed from XRD analysis. An evident phase transition from the orthorhombic to the
tetragonal phase is observed when the BaTiO3 nanoparticles are annealed at 100C and tetragonal phase
along with orthorhombic phase is observed for all other annealed samples. Annealing at 800 oC resulted in
stabilization of pure rhombohedral phase. Surprisingly, dominating XRD peaks (NP) were observed in
annealed samples at 100 – 400 oC, often related to BaCO3 in literature, even though barium (II) chloride,
titanium (IV) chloride and NaOH were used as the precursors. The nanoparticles were further characterized
by SEM and TEM, which showed uniform spherical shaped nanoparticles transformed to rod morphology
with increase in agglomeration of particles. Raman Spectroscopy analysis showed the presence of
characteristic tetragonal and orthorhombic Raman bands and the annealed materials exhibited similar
characteristics as that of as-synthesized material, in addition, it shows an additional sharp peak around
690 cm-1, identified as corresponding to hexagonal phase in literature, suggests new phase transition or
phase separation in BaTiO3. These results coincide well with UV and PL spectrum analysis. All the samples
demonstrate non-linear optical properties demonstrating second harmonic generation. Identification of
the NP-XRD peaks and influence of annealing on the second harmonic generation are presented in detail.
Finally, Dye-sensitized solar cell with BaTiO3 as photo anode will be fabricated and its IV characteristics will
be studied.
