Structure and negative thermal expansion in the PbTiO3-BiFeO3 system

The structures of (1-x)PbTiO3-xBiFeO(3) (x=0.3 and 0.6) were investigated by means of the neutron powder diffraction. A splitting shift between Fe and Ti atoms was found along the c axis in 0.7PbTiO(3)-0.3BiFeO(3); however, this splitting does not appear in 0.4PbTiO(3)-0.6BiFeO(3). The tetragonal phase of PbTiO3-BiFeO3 exhibits a large spontaneous polarization. The negative thermal expansion of PbTiO3 is significantly enhanced in a wide temperature range by the BiFeO3 substitution. The average bulk thermal expansion coefficient of 0.4PbTiO(3)-0.6BiFeO(3) is < over bar > a </over bar >(v)=-3.92x10(-5) degrees C-1, which is much strong in the known negative thermal expansion oxides. (c) 2006 American Institute of Physics.