  Epitaxial (001)-, (118)-, and (104)-oriented Nd-doped Bi4Ti3O12 films have
been grown by pulsed-laser deposition from a Bi4-xNdxTi3O12 (x=0.85) target on
SrRuO3 coated single-crystal (100)-, (110)-, and (111)-oriented SrTiO3
substrates, respectively. X-ray diffraction illustrated a unique epitaxial
relationship between film and substrate for all orientations. We observed a
strong dependence of ferroelectric properties on the film orientation, with no
ferroelectric activity in an (001)-oriented film; a remanent polarization, 2Pr,
of 12 microC/cm2 and coercive field, Ec, of 120 kV/cm in a (118)-oriented film;
and 2Pr = 40 microC/cm2, Ec = 50 kV/cm in a (104)-oriented film. The lack of
ferroelectric activity along the c-axis is consistent with the orthorhombic
nature of the crystal structure of the bulk material, as determined by powder
neutron diffraction.
