Low-temperature sintered (Na1/2Bi1/2)TiO3-based incipient piezoceramics for co-fired multilayer actuator application

Low-temperature sintered (Na1/2Bi1/2)0.935Ba0.065Ti0.975(Fe1/2Nb1/2)0.025O3 (NBT-BT-0.025FN) lead-free incipient piezoceramics were investigated using high-purity Li2CO3 as sintering aids. With the ≤0.5 wt% Li2CO3 addition, the introduced Li+ cations precede to enter the A-sites of the perovskite lattice to compensate for the A-site deficiencies. Once the addition exceeds 0.5 wt%, the excess Li+ cations will occupy B-sites and give rise to the generation of oxygen vacancies, which accelerate the mass transport and thus lower the sintering temperature effectively from 1100 °C down to 925 °C. It was also found that a small amount of Li+ addition has little effect on the phase structure and electromechanical properties of the system, but overweight seriously disturbs these characteristics because of the large lattice distortion. The sintered NBT-BT-0.025FN incipient piezoceramics with 1.25 wt% Li2CO3 addition at 925 °C provides a large strain of 0.33% and a corresponding large signal piezoelectric coefficient d*33 of 550 pm/V at 60 kV/cm, indicating this system is a very promising candidate for lead-free co-fired multilayer actuator application.