FERROELECTRICS, vol.302, pp.525-529, 2004 (SCI-Expanded)
Optical absorption in the IR region has been recorded and first-principles computations have been done for some Fe contining perovskites. The IR absorption reveals a broad peak at about 11000 cm(-1). First principles computations established that BaFe1/2 Nb1/2O3 is not ferroelectric, but PbFe1/2Nb1/2O3 does have a ferroelectric instability. These data confirm that the large dielectric permittivity found in BaFe1/2Nb1/2O3 is not due to a ferroelectric phase transition but rather because of extrinsic effects.