Structural, dielectric, and piezoelectric properties of fine-grained NBT-BT0.11 ceramic derived from gel precursor

(Na1/2Bi1/2)TiO3 doped in situ with 11 inol% BaTiO3 (NBT-BT0.11) powders were synthesized by a sol-gel method, and the electrical properties of the resulting ceramics were investigated. The powders consisting of uniform and fine preliminary particles of about 50 nm were prepared by calcining the gel precursor at 700 degrees C. (Na1/2Bi1/2)(0.89)Ba0.11TiO3 ceramics, sintered at temperatures up to 1150 degrees C have a rhombohedral symmetry while the ceramic sintered at 1200 degrees C exhibits a tetragonal crystalline structure. The ceramics show high dielectric constant (epsilon(r) similar to 5456), dielectric loss of 0.02, depolarization temperature T-d similar to 110 degrees C and temperature corresponding to the maximum value of dielectric constant T-m similar to 262 degrees C. The dielectric constant (epsilon(33)) and the piezoelectric constant (d(33)) attain the maximum values of 924 and 13 pC/N, respectively, while the electromechanical coupling factor (k(p)) value is 0.035. The NBT-BT0.11 ceramics derived from sol-gel present high mechanical quality factor (Q(m) similar to 860). The dielectric and piezoelectric properties values of NBT-BT0.11 ceramics derived from sol-gel are smaller than those of samples produced by the conventional solid state reaction method, due to the grains size and oxygen vacancies that generate dipolar defects. (C) 2012 Elsevier Ltd. All rights reserved.