Strain characteristics and electrical properties of [Li0.055(K0.5Na0.5)0.945](Nb1-xTax)O3 ceramics

[Li-0.055(K0.5Na0.5)(0.945)](Nb1-xTax)O-3 (0.05 <= x <= 0.25) ceramics were prepared by the partial sol-gel (PSG) method to improve the microstructure homogeneity of Ta5+ ion and were compared to those prepared by the conventional mixed oxide (CMO) method. For the PSG method, Ta(OC2H5)(5) was directly reacted with calcined [Li-0.055(K0.5Na0.5)(0.945)]NbO3 powders and the specimens sintered at 1100 degrees C for 5 hrs showed a single phase with a perovskite structure. Compared to the specimens prepared by conventional mixed oxide powders, the relative ratio of tetragonal phase to orthorhombic phase of the sintered specimens prepared by Ta(OC2H5)(5) was larger than that of the sintered specimens prepared by Ta2O5. The electromechanical coupling factor (k(p)), piezoelectric constant (d(33)) and dielectric constant (epsilon(T)) of the sintered specimens were increased with Ta5+ content. These results could be attributed to the decrease of the orthorhombic-tetragonal polymorphic phase transition temperature (T0-t), which could be evaluated by oxygen octahedral distortion. Strain of the sintered specimens prepared by the PSG method was higher than that of specimens prepared by the CMO method due to the increase of relative density. The effects of crystal structure on the strain characteristics of the specimens were also discussed.