I4/mcm -> Pm3m phase transition in Sr0.5Ba0.5HfO3.delta

The effect of partial substitution of cations in AMO(3) compounds have been studied because the physical properties and applications of these material s can be improved. In particular we are interested in the Sr1-xBaxHfO3 fami ly. In SrHfO3 the phase transition to cubic structure has been observed to occur when the angle between two consecutive oxygen octahedra tends to zero . Instead in BaHfO3 no phase transition was observed. These facts were attr ibuted to depend on the atomic radius of A cation. In this contribution the study of Sr0.5Ba0.5HfO3 oxide is shown. The compound was prepared by the h igh temperature solid state reaction method and analyzed by X-ray diffracti on and Perturbed Angular Correlation (PAC) Spectroscopy at different temper atures. Diffraction studies revealed that about 400-420 degrees C a structu ral phase transition from I4/mcm to Pm3m occurred by tending to zero the ro tation angle. By PAC this transition was also observed. In the cubic phase the electric field gradient EEG measured were produced by defects. The same model applied to interpreted the results of BaTi1-xHfxO3 and the atomic po sitions determined by X-ray diffraction were used. This calculation reprodu ces reasonably the temperature dependence of the EFG measured by PAC.