Study of new relaxor materials in BaTiO3-BaZrO3-La2/3TiO3 system

Dielectric studies were performed on new lead-free ceramics derived from BaTiO3 by iso-valent and off-valent substitutions in both octahedral and dodecahedral sites and having the compositions (Ba1-xLa2x/3)(Ti1-yZry)O-3, with 0 <= x <= 0.35 and 0 <= y <= 0.35. The dielectric permittivities of samples measured as a function of temperature and frequency showed relaxor or classical transition phase. The classical ferroelectric behaviour is exhibited by compositions close to the binary systems BaTiO3-La2/3TiO3 (BT-LT) or BaTiO3-BaZrO3 (BT-BZ), as long as the substitution rates remained small (x < 0. 15 and y < 0.30). The relaxor behaviour occurred in compositions BT-LT BT-BZ and BT-LT-BZ which deviated strongly from BaTiO3. The values of peak temperature TC (or Tm) decreased with increasing x and/or y, being less sensitive to y variations than that of x. In the relaxor zone, the decreasing of Tm is accompanied with an increasing of the characteristic Delta T-m, in BT-LT (x >= 0.15) and BTLT-BZ (x = 0.10; 0.05 <= y <= 0.35) solid solutions. For the best relaxor material of composition (Ba0.90La0.2/3)(Ti0.95Zr0.05)O-3, the dielectric constant (E) and the peak temperature Tm exhibited interesting values (22000 and 200 K, respectively) if compared to other r similar perovskite-like materials. Moreover, such ceramics are lead-free and could fit to environmental friendly requirements in the case of applications. (c) 2005 Elsevier SAS. All rights reserved.