Diffuse phase transition in the (La0.03Sr0.255Ba0.7)(Nb2-yTiy)O-6.y/2 ferroelectric ceramic system

The effect of the titanium cation as a doping element in the diffuse phase transition of the (Sr0.255La0.03Ba0.7)(Nb2-yTiy)O6-y/2 ferroelectric cerami c system is studied. Far from the transition temperature, a Curie-Weiss beh avior of the dielectric permittivity with temperature is observed with stro ngly broadened curves in all cases, however, a non Curie-Weiss behavior abo ve the transition temperature is observed. The diffuseness coefficient (del ta) was calculated using Isupov's relation and by a more realistic model as suming a Gaussian distribution for the transition temperatures, in a temper ature interval around the maximum permittivity temperature. The conditions under which each expression can be used are discussed.