Résumé: 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)O3, with 0[less-than-or-equals, slant]x[less-than-or-equals, slant]0.35 and 0[less-than-or-equals, slant]y[less-than-or-equals, slant]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 BaTiO3La2/3TiO3 (BT-LT) or BaTiO3BaZrO3 (BT-BZ), as long as the substitution rates remained small (x and y). 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]Tm, in BT-LT (x[greater-or-equal, slanted]0.15) and BT-LT-BZ (x=0.10; 0.05[less-than-or-equals, slant]y[less-than-or-equals, slant]0.35) solid solutions. For the best relaxor material of composition (Ba0.90La0.2/3)(Ti0.95Zr0.05)O3, the dielectric constant () and the peak temperature Tm exhibited interesting values (22 000 and 200 K, respectively) if compared to other similar perovskite-like materials. Moreover, such ceramics are lead-free and could fit to environmental friendly requirements in the case of applications.

Langue: Anglais