Effect of ZnO Nanoparticles on the Sintering Behavior and Physical Properties of Bi(NaK)TiO Lead-Free Ceramics

Sintered Bi(NaK)TiO + x wt.% ZnO nanoparticle (BNKT–xZnO) ceramics have been fabricated by conventional annealing with the aid of ultrasound waves for preliminary milling. Because of the presence of the liquid BiO–ZnO phase at the eutectic point of 738°C, the sintering temperature decreased from 1150°C to 1000°C, and the morphology phase boundary of BNKT–xZnO ceramics can be clarified by two separated peaks at (002) and (200) of 2θ in the x-ray diffraction (XRD) patterns. The improvement of ferroelectric properties has been obtained for BNZT–0.2 wt.% ZnO ceramics by the increase of remanent polarization up to 20.4 μC/cm and a decrease of electric coercive field down to 14.2 kV/cm. The piezoelectric parameters of the ceramic included a piezoelectric charge constant of d = 78 pC/N; electromechanical coupling factors k = 0.31 and k = 0.34, larger than the values of 42 pC/N, 0.12 and 0.13, respectively, were obtained for the BNKT ceramics.