Improved electrical properties of Co-doped 0.92NBT-0.04KBT-0.04BT lead-free ceramics

The (1-2x)NBT-xKBT-xBT ternary piezoelectric system has been extensively studied in recent years. However, its electrical performance is far inferior to lead-based counterparts, and could not meet the requirements for practical applications. In this contribution, the 0.92NBT-0.04KBT-0.04BT (abbreviated as NKBT4) ceramics were prepared by traditional solid-state method. The effects of doped cobalt content on the structure and electrical performance of NKBT4 ceramics were studied systematically. The content of Co2O3 affects the average grain size, maximum dielectric constant, piezoelectric properties and the ferroelectric responses of the ceramics. It was found that the introduction of cobalt did not affect the phase structure of the ceramics, but is beneficial for the improvement of the dielectric and piezoelectric properties. When x=0.2, the piezoelectric coefficient (d(33)) is around 130 pC/N, which is greatly improved compared to pure NKBT4 ceramics. Besides, a relatively high dielectric constant (epsilon(r)=1150) was obtained at the same composition. This work paves a new way for the further development of high performance lead-free piezoelectric ceramics.