Low temperature sintering of Bi0.5Na0.5TiO3 based ceramics

Bi-based piezoelectric ceramics are a good candidate to replace lead zirconate titanate (PZT) for use as multilayer actuators (MLA) in diesel fuel injectors due to their moderate piezoelectric properties at room temperature. Current MLA use PZT with copper internal electrodes and require sintering at low temperature and controlled oxygen atmosphere. A combination of Bi₂O₃, CuO, Li₂CO₃, ZnO, and B₂O₃ are added to 0.88Bi_1/2Na_1/2TiO₃ - 0.08Bi_1/2K_1/2TiO₃ - 0.04BaTiO₃ (BNT-BKT-BT) for sintering at 900°C in air or controlled atmosphere. The low temperature sintered ceramics have similar room temperature properties compared to ceramics sintered at 1150°C. Low temperature sintering results in softening of piezoelectric properties and lower depolarization temperature. Sintering in controlled oxygen atmosphere enables the Bi-based ceramic to be co-fired with Cu electrodes. The co-fired ceramic with Cu electrodes demonstrates the feasibility of lead-free BNT-based multilayer actuators with Cu base metal electrodes.