THERMAL-EXPANSION STUDIES IN THE LEAD IRON NIOBIATE - LEAD TITANATE SYSTEM

Compositions in the solid solution series {Pb(Fe0.5Nb0.5)O-3}(1-x) - { PbTiO3}(x) (x = 0 --> 1) were prepared by solid state reaction. The ph ase transition from rhombohedral/tetragonal to cubic structure has bee n studied as a function of x by differential thermal analysis, high te mperature x-ray diffraction and dilatometry in the temperature range 2 98-773K. Dielectric measurements and thermal expansion coefficients of the x = 0.2 composition indicate that the relaxor type behaviour of l ead iron niobate is extended up to 453K.