Effect of the lanthanum concentration on the physical properties of the (Bi0.5Na0.5)0.92Ba0.08-3x/2LaxTiO3 ceramic system

The influence of lanthanum concentration on the structural, ferroelectric and dielectric properties of BNT-BT ceramic compounds with a composition close to the morphotropic phase boundary (Bi0.5Na0.5)0.92Ba0.08-3x/2LaxTiO3 (x = 0, 1, 2 and 3 at.%) has been studied. The structural properties reveal the coexistence of both ferroelectric (P4mm) and antiferroelectric (P4bm) tetragonal phases for the lanthanum-free system. Nonetheless, for the La3+ modified samples, both antiferroelectric tetragonal (P4bm) and ferroelectric rhombohedral (R3c) phases coexist. On the other hand, slim-like hysteresis loops for the x = 1 at.% La3+ concentration have been observed, suggesting a higher stability of the antiferroelectric phase. However, for the other compositions (including the lanthanum-free sample) the P-E hysteresis loops suggested a higher stability of the ferroelectric phase. The dielectric response has shown the presence of three anomalies in the entire analyzed temperature range, which have been associated to different phase transitions with an important influence of the lanthanum content.