Effects of Bi2O3, Sm2O3 content on the structure, dielectric properties and dielectric tunability of BaTiO3 ceramics

(1-x)BaTiO3-x (Bi2O3, Sm2O3) (BT-BS, x=0.1, 0.15, 0.2, 0.25, 0.3) ceramics were prepared by traditional solid phase sintering method. The effects of structure, temperature and frequency on dielectric tunability, ferroelectric relaxation characteristics and dielectric loss were analyzed. Phase analysis by XRD showed that the main crystal phase was BaTiO3 perovskite structure, in addition to the second phase of Bi7.68Ti0.32O12.16 was also generated. The surface morphology was analyzed by SEM, it was found that the generation of second phase and the porosity decreased with the increase of BS content. At the same time, the increase of Sm3+ promoted the growth of crystal particles. The dielectric constant-temperature curve gradually became flat, which indicated that the relaxation characteristics of the ferroelectric ceramic gradually appear. The Curie temperature point gradually decreased with the doping of the BS. The relationship between dielectric loss and temperature showed that the dielectric loss increased when the temperature over 150 degrees C. This is mainly related to relaxation polarization at high temperature. Under the action of DC applied electric field and room temperature, dielectric loss and dielectric constant decreased with the increase of BS content. Meanwhile, dielectric tunability was improved when composite phase appeared. The maximum dielectric tunability (E=50 kV/cm, 10 kHz) was 58.4% at x=0.25.