The Preparation And Properties Of Bi₃Fe_0.5Nb_1.5O₉ Ceramics By Spark Plasma Sintering

Dense Bi3Fe0.5Bi1.5O9 ceramics were prepared by spark plasma sintering in the present work.The effect of sintering temperature and calcination temperature on the structure,dielectric properties and ferroelectric properties were investigated.The effect of Co-doping on the properties of Bi3Fe0.5Bi1.5O9 ceramics was also studied.Dense Bi3Fe0.5Bi1.5O9 ceramics were prepared by spark plasma sintering successfully.The relative density of the Bi3Feo.5Nb1.5O9 ceramics sintered at 700°C for 5min with a pressure of 30MPa by SPS is over 98%.The result of XRD showed that the structure of Bi3Feo.5Nb1.5O9 samples is orthogonal structure.Compared to the conventional sintering method,Spark plasma sintering method prepared denser ceramics at lower temperatures in much shorter time(over 100°C lower than the traditional sintering method).Bi3Feo.5Nb1.5O9 ceramics prepared by SPS have higher density and better grain morphology.Different calcination temperature and sintering temperature affected the crystal structures of Bi3Fe0.5Nb1.5O9.When the sintering temperature was 700°C,raising the burning temperature from,impurities in crystals disappeared as the calcination temperature increases from 750°C to 850°C;When the calcination temperature was 850°C,the crystalinity of Bi3Feo.5Nb1.5O9 ceramics was modified,while the dielectric constant and dielectric loss decreased as the sintering temperature increased.Dielectric constant and dielectric loss of Bi3Fe0.5Nbl.5O9 ceramics decreased as the frequency increased,and increased as the temperature rise.The dielectric relaxation of Bi3Fe0.5MNb1.5O9 prepared at 700°C were identified,and Ea=0.40eV.Description dielectric relaxation in the temperature range of 250 to 350K was connected to electronic ferroelectric caused by Fe2+/Fe3+ ion mixing structure electronic ordering.We observed hysteresis cycle in the Bi3Feo.5Nb1.5O9 prepared at 700°C,but the ferroelectric properties was very weak,Pr=0.0luc/cm2,Ec=0.72KV/cm?When doped with a small amount of Co in BFN ceramic,the crystal structures almost do not change.When small amounts of Co-doped,the dielectric constant and dielectric loss of the crystal nearly did not change.When the doping amount of Co was 0.05 or more,there was a new dielectric relaxation mechanism in 300K-450K.A small amount of Co doped in BFN ceramics did not change the ferroelectric properties,and it is still very weak,but when the x=0.25,the lattice structure changes and the ferroelectric properties change a lot.The result is Pr=0.63 uc/cm2,Ec=7.58Kv/cm when x=0.25,but under the same test conditions,Pr=0.002 uc/cm2,Ec=0.228 Kv/cm when it is pure BFN ceramic.