Diffuse phase transition of the Sr0.3-3y/2LayBa0.7Nb2O6 ceramic system

Abstract

The effect of Lanthanum cation doping in the diffuse phase transition of the Sr0.3-3y/2La yBa0.7Nb2O6 ceramic system is studied for y = 0.01, 0.03 and 0.05. For these compositions, the transition temperature T-c shifts towards higher values with increasing frequency and the temperature dependence of the electrical permittivity presents strongly broadened curves which suggest a non Curie-Weiss behavior near the transition temperature for temperatures far from T-c. The diffuse phase transition coefficient (delta) was also determined and its values lead us to conclude that the degree of disorder in the system increases with the presence of the Lanthanum cation. This result is corroborated by calorimetric measurements, where an increase in entropy with the Lanthanum concentration is also found.