Superior Ultra-high Temperature Multilayer Ceramic Capacitors Based on Polar Nanoregion Engineered Lead-free Relaxor

Abstract The assembly of high-temperature electronic equipment places great demands on ultra-high temperature multilayer ceramic capacitors (UHT-MLCCs). However, the relatively low dielectric constant and inferior reliability associated with the protruding ferroelectric phase transition for existing dielectric materials have hindered the development of UHT-MLCCs. Here, these concerns have been addressed by the strategy of composition modulation of different types of polar nanoregions (PNRs) in bismuth-based perovskite relaxor. A new lead-free dielectric system (1-x)(0.8Na0.5Bi0.5TiO3-0.2K0.5Bi0.5TiO3)-xBi(Mg2/3Nb1/3)O3 (NBT-KBT-xBMN) dominated by P4bm PNRs has been built and the corresponding UHT-MLCCs with 70Ag/30Pd inner electrodes are fabricated by tape casting and cofiring processes. A record-high dielectric constant (er = 1800 ± 15%) together with low dielectric loss (tanδ ≤ 0.025) is achieved over a wide range of 100 °C to 440 °C for NBT-KBT-0.2BMN MLCC, which consists of nine dielectric layers with the single-layer thickness of 70 μm. The excellent results suggest that NBT-KBT-0.2BMN MLCC can provide realistic solutions for next-generation UHT-MLCC applications and the material design strategy can be generalized for the construction of more high performance capacitor dielectrics.