It is very useful to grow epitaxial PbTiO3 films on Si substrates for
applications in integrated devices. At high growth temperatures, this
leads to the formation of an intermediate metastable Pb2-xTi2-ySix+yO6
phase (with a pyrochlore structure) and the consequent partial incorp
oration of Si into the PbTiO3 lattice. To understand the effect of Si
on the ferroelectric characteristics of the material, it is important
to determine the position and state of aggregation of Si in the PbTiO3
lattice. We have attempted to investigate this aspect by a neutron di
ffraction study of silicon doped ceramic lead titanate. Our results in
dicate that the silicon may exist in the form of a glassy lead silicat
e phase dispersed at the grain boundaries. Some of the Si atoms may al
so occupy interstitial positions in the lattice.