Effects of pyrolysis temperature on structural, Raman, and infrared properties of perovskite PbTiO₃ nanotubes

In this work, we investigated the effects of the pyrolysis temperature on the structural, Raman, and infrared properties of PbTiO₃ nanotubes (PTO-NTs). The PTO-NTs were synthesized by spin coating a sol-gel solution on porous anodic alumina membranes, followed by the pyrolysis step at 400 − 600 ℃. Then, PTO-NTs were finally crystallized at 600 − 700 ℃ in an oxygen atmosphere to get the perovskite phase. The PTO-NTs had an outer diameter of about 420 nm and a wall thickness of about 10 nm. X-ray diffraction patterns showed that the tetragonality (c/a) increased from 1.019 to 1.028 as the pyrolysis temperature was increased from 400 to 600 ℃. Raman spectroscopy showed that the phonon modes of A₁(nTO) and E(nTO) increased with a redshift of the A₁(3TO) mode as the pyrolysis temperature was increased. In the Fourier-transform infrared spectra of PTO-NTs embedded in the porous anodic alumina membrane, the transmittance of the band at 499 cm⁻¹ increased as the pyrolysis temperature was increased, which might be due to an increase in the tetragonality.