Effects of Bi_(0.5)Na_(0.5)TiO_3 Addition on the Dielectric Properties of BaTiO_3-Nb_2O_5-ZnO System

The effects of Bi_(0.5)Na_(0.5)TiO_3(BNT)doping on the dielectric properties and microstruc- tures of BaTiO_3(BT)-Nb_2O_5-ZnO ternary system were investigated.TheΔC/C_(25℃)values at low temperature(-55℃)decrease with increasing BNT content,but the AC/C_(25℃)values at high temper- ature(150℃)and the Curie temperature(T_c)show continuous enhancement.BaTiO_3 ceramic doped with 1.0wt% and 2.5wt% BNT are satisfied with the EIA X8R specification.SEM indicates that the BaTiO_3 ceramics are composed of fine grains and secondary phase grains.Moreover,the proportion of the secondary phase grains increases as BNT contents increase.XRD analyses prove that the fine grains are BaTiO_3 and the secondary phase grains are identified to be CaB_2Si_2O_8 and NaBiTi_6O_(14).The formation of the strip-shaped secondary phase of CaB_2Si_2O_8 and NaBiTi_6O_(14)which alters the internal stress system of BaTiO_3 ceramics is presumed to be the factor that shifts the T_c to higher temperature and improves the temperature characteristic of BaTiO_3 ceramics.