Synthesis and characterization of BaTiO₃-based X9R ceramics

Abstract

The effects of (Na_0.5Bi_0.5)TiO₃ (NBT) and MgO addition on the dielectric properties and microstructures of BaTiO₃ (BT) ceramics were investigated. NBT was first added to Nb₂O₅-doped BT system. As NBT content increases from 0 to 0.2 mol, the Curie temperature of the systems shifts to high temperatures and dielectric constant peak at T _c is suppressed evidently. The variation of capacity (ΔC/C _20 °C (%)) of the system at 200 °C decreases with increasing NBT content from 0.1 to 0.2 mol, but that of −55 and 125 °C increases monotonously. The stable temperature characteristics of the dielectric properties improved by NBT doping would be connected with the distortion and deformation of the structure induced by substitution of Na⁺ and Bi³⁺ into Ba sites. MgO was employed to further flatten the ΔC/C _20 °C–T curve. It is very helpful for this ceramic system to satisfy the requirement of EIA-X9R specification on ΔC/C _20 °C and still keep a satisfied dielectric constant. The addition of MgO improved effectively the temperature stability of the dielectric properties. Changes of the crystalline structure and microstructure induced by MgO doping might contribute to these improvements.