关键词: X8R, 钛酸钡, 钛酸铋钠, 多层陶瓷电容器

Abstract: The effects of Bi_0.5Na_0.5TiO₃ (BNT) doping on the dielectric properties and microstructures of BaTiO3 (BT)-Nb2O5-ZnO ternary system were investigated. The Δ C/C_25℃ values at low temperature (-55℃) decrease with increasing BNT content, but the Δ C/C_25℃ values at high temperature (150℃) and the Curie temperature (T_c) show continuous enhancement. BaTiO₃ ceramic doped with 1.0wt% and 2.5wt% BNT are satisfied with the EIA X8R specification. SEM indicates that the BaTiO₃ 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 BaTiO₃ and the secondary phase grains are identified to be CaB₂Si₂O₈ and NaBiTi₆O₁₄. The formation of the strip-shaped secondary phase of CaB₂Si₂O₈ and NaBiTi₆O₁₄ which alters the internal stress system of BaTiO₃ ceramics is presumed to be the factor that shifts the T_c to higher temperature and improves the temperature characteristic of BaTiO₃ ceramics.

Key words: X8R, barium titanate, sodium bismuth titanate, multilayer ceramic capacitors