DIFFUSE PHASE-TRANSITION IN PB(FE0.5NB0.5)O3-BASED SOLID-SOLUTIONS

Temperature dependence of permittivity in ceramic (1 - x)Pb(Fe0.5Nb0.5)O3 - xABO3, where A = Ca, Sr, Pb, Ba; B = (Fe0.5Nb0.5), Ti, Sn, Hf, Zr, Ge, Ce; x less-than-or-equal-to 0.09 were studied. The correlation between the phase transition diffuseness and the rate of Curie temperature variation with composition predicted by the composition fluctuations model was absent. The diffuseness at certain x grows with the increase of difference between substituting B ion radius and the radius of Nb ion, but is practically independent of the type of substituting A-ion. These facts are consistently explained in the frame of the new model [Bokov A.A., Ferroelectrics, (1992) 131, 49].