Dielectric properties of low-temperature co-fired capacitor ceramics and MLCC devices with Ag inner electrodes

Low-temperature sintered 0.99((1−x)Bi_0.5Na_0.5TiO₃-xNaNbO₃)-0.01Sr_0.8Na_0.4Nb₂O₆ (100xNN, x = 0.25 and 0.30) ceramics and MLCC were successfully prepared, and the dielectric properties were systematically investigated. The dielectric permittivity at 25 °C (ε′₂₅ °_C) of 25NN ceramic is 1088, and the dielectric variation is small between −88 °C and 400 °C (|△ε′/ε′₂₅ °_C| ≤ 15%, △ε′=ε′-ε′₂₅ °_C). The dielectric loss tangent (tanδ) of 25NN ceramic is less than 0.02 between -65 °C and 358 °C. The MLCC with 25NN ceramic dielectrics and Ag inner electrode also has excellent dielectric stability, of which |△ε′/ε′₂₅ °_C| is less than 15 % between −100 °C and 400 °C, and the dielectric loss is less than 0.02 between −88 °C and 373 °C. All these results indicate that the low-temperature sintered MLCC with Ag inner electrodes is a promising capacitor in automobile engines and aerospace fields, where the usage temperature is often above 300 °C.