Preparation and dielectric properties of BaTiO3-based X8R ceramics co-doped with BIT and CBS glass

The effects of Bi4Ti3O12 (BIT) on phase purity and dielectric properties of BaTiO3 (BT) ceramics have been investigated. Results show that BT samples doped with 1–3 mol% BIT adopt a single phase. However, secondary phase Bi2Ti2O7 is observed when BIT content exceeds 3 mol%. Tetragonality and the Curie temperature (TC) firstly increase and then decreases with an increase in BIT content. The 3 mol% BIT-doped BT ceramic sintered at 1,250 °C exhibits good dielectric properties of εr = 2,692, tan δ = 0.0152, ρv = 5.8 × 1012 Ω cm, and the variation of dielectric constant as compared with that at room temperature is about −20 % at −55 °C and less than 11 % at 150 °C. It is found that the addition of calcium borosilicate glass (CBS) in BT-BIT ceramics can effectively lower the sintering temperature from 1,250 to 1,050 °C and further enhance the capacitance temperature stability. The permittivity decreases with an increase in CBS content from 1 to 10 wt%. Secondary phase BaBi4Ti4O15 exists in the CBS doped BT-3BIT systems. All of CBS doped samples satisfy the X8R specification. Typically, the sample with 3 wt% CBS has εr = 1,789, tan δ = 0.0115, ρv = 9.67 × 1012 Ω cm. The variation of permittivity as compared with that at room temperature is about −12 % at −55 °C and less than ± 11 % at 150 °C. The as-prepared materials have great potential as EIA X8R-type multilayer ceramic capacitors.