Si induced size effects in ferroelectric PbTiO3

Physical properties of PbTiO3 in the presence of Si are investigated in det ail. Polycrystalline bulk samples with nominal composition of (Pb1-xSix) (T i1-xSix)O-3, where x varies from 0.01 to 0.25, are synthesized using the co precipitation route. The presence of Si in the matrix leads to a reduction in coherently diffracting domain size (d(XRD)). The observed reduction in t he ferroelectric distortion in the lattice c/a, ferroelectric transition te mperature T-c and shift in Raman lines of PbTiO3 with increase in Si conten t are attributed to the Si induced finite size effect. However, at higher c alcination temperatures, the material exhibits properties similar to pure, undoped, bulk PbTiO3. There is no evidence of change in crystal structure a nd ferroelectric nature of PbTiO3 due to the presence of Si. Our data sugge sts that Si, which is diffused out of PbTiO3 perovskite lattice, is likely to reside in the grain boundary region in an as yet unidentified chemical f orm. (C) 2000 American Institute of Physics. [S0021-8979(00)03301-6].