Effect of Si doping in ferroelectric PbTiO3

The growth of ferroelectric PbTiO3 thin film on Si is severely hampered by the formation of non-ferroelectric Pb2Ti2O6 pyrochlore phase due to diffusion of Si in the film. Although Pb2Ti2O6 phase converts to perovskite PbTiO3 phase at higher annealing temperature, the perovskite phase thus formed obviously contains Si in it. It is therefore interesting to investigate the physical properties of Si doped PbTiO3. Chemically homogeneous Si doped PbTiO3 bulk samples are synthesized using co-precipitation route. Stoichiometry is confirmed by Rutherford Backscattering spectroscopy. X-ray analysis indicates that the c/a ratio and domain size decreases with increase in Si concentration at a given calcination temperature. Differential Scanning calorimetry reveals a reduction in ferroelectric Tc with increase in Si. Raman spectra are suppressed for lower Si concentration but at higher concentration only line shifts are observed. Over all, these results point to a development of stress on the PbTiO3 lattice due to presence of Si. There is also an indication of an optimum concentration of Si in PbTiO3 at which ferroelectric properties of PbTiO3 are preserved. (author)