Synthesis, characterization and dielectric properties of Ba_(1-x)La_xTi_(1-x/4)O_3 powders and ceramics synthesized by sol-gel method

摘要

In the present study polycrystalline Ba_(1-x)La_xTi_(1-x/4)O_3 (x = 0.00, 0.015, 0.025, 0.035, 0.045 and 0.055) powders were synthesized using sol-gel route at 850 ℃ for 4 h. Calcined powders were sintered in air at 1300 ℃ for 6 h to make dense ceramics. XRD studies confirmed the tetragonal crystal structure of the x = 0.00-0.035 compositions at room temperature of the Ba_(1-x)La_xTi_(1-x/4)O_3 ceramic samples. A cubic symmetry (Pm3m) was observed for the x ＞ 0.035 compositions around room temperature. SEM studies showed that the average grain size was decreased with an increase in La content. The dielectric constant (ε_r) and dielectric loss (tan δ) of the Ba_(1-x)La_xTi_(1-x/4)O_3 ceramics were investigated in the frequency regime (10 kHz-1 MHz). The highest magnitude of ε_r and tan δ around room temperature at 10 kHz was recorded for the x = 0.025 composition as 14,468 and 0.07, respectively. The Curie temperature (T_c) was shifted to low temperatures with an increase in La content. Complex impedance analysis confirmed the grain boundary and bulk contribution in the conduction mechanism for the x = 0.00 composition. The x ≥ 0.015 compositions showed only grain boundary contributions. The total resistance of sintered samples was decreased with an increase in temperature for the Ba_(1-x)La_xTi_(1-x/4)O_3 ceramics, showing a typical ceramic behavior.