Negative thermal expansion in the PbTi1-xFexO3 system

Multiferroic magnetoelectric PbTi1-xFexO3 compounds were prepared using a solid-state reaction method in the composition range 0 <= x <= 0.15. The temperature dependence of lattice parameters of PbTi1-xFexO3 was determined from high-temperature X-ray diffraction. The average volumetric thermal expansion coefficient of the tetragonal phase increases from -1.99 x 10(-5) degrees C-1 for PbTiO3 to -1.13 x 10(-5) degrees C-1 for PbTi0.90Fe0.10O3. The negative thermal expansion and the Curie temperature (T,) of PbTiO3 are reduced by the introduction of Fe. Raman spectral measurements show a softening behaviour for A(1)(1TO) and A(1)(2TO) of PbTi(1-x)Fex(.)O(3) with increasing Fe concentration, which means that the decrease in both T, and c/a is due to the reduced spontaneous polarization. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim