The crystal structure and the phase transition of (1-x)Pb(Yb1/2Ta1/2)O-3-xPb(Fe1/2Ta1/2)O-3 solid solutions in the antiferroelectric range for 0 less than or equal to x less than or equal to 0.10 have been studied by the dielectric constant measurements, E-P hysteresis measurements, X-ray diffraction and transmission electron microscopy (TEM). In the composition region x less than or equal to 0.10, the dielectric dispersion which is the secondary phase transition point of pure PYT remains and it exhibits slim loop which means that the solid solution is ferroelectric at low temperatures. From the X-ray diffraction analysis of the superlattice structure of (1-x)PYT-xPFT solid solutions, it is found that there are no basic structural changes as x increases up to x = 0.10. But in the TEM analysis, the antiferroelectric phase is shown to coexist with the ferroelectric phase below the secondary phase transition temperature. In the selected area diffraction pattern (SADP), an intermediate incommensurate phase is observed. (C) 2003 Elsevier Ltd. All rights reserved.