Effect Of Niobium Doping On The Mechanical And Electrical Properties Of (Na_0.85K_0.15)_0.5Bi_0.5TiO₃Thin Films

Since the volatility of lead in lead zirconate titanate （PZT） causes environmentalpollution, people have been looking for lead-free ferroelectric materials to replace PZT.Sodium bismuth titanate (Na_0.5Bi_0.5TiO₃,NBT) is an excellent lead-free ferroelectric materials.But NBT has the defects of high coercive field and large leakage current, which restrict itsuse. Therefore, we want to improve the performance of NBT thin film by doping. Firstly,A-site potassium-doped NBT thin films was studied and the morphotropic phase boundary（MPB） of （Na（1-x）Kx）_0.5Bi_0.5TiO₃（NKBT100x） were determined. Then, B-site niobium-dopedNKBT15thin films were studied. The main content is showed below:1. NKBT100x （x=0.11,0.13,0.15,0.17,0.19） thin films were prepared by metal-organicdecomposition （MOD）, and the phase structures, surface morphologies, ferroelectricproperties, piezoelectric properties and dielectric properties at high temperature of theNKBT100x thin films have been studies. The XRD results show that all the thin films are ofsingle-phase perovskite structure and there is intimate coexistence of two phases in thepotassium content range x=0.13-0.17. The MPB of NKBT100x thin films located x=0.13-0.17,which was identified by multi-peak fitting in grazing incidence X-ray diffraction patterns. TheNKBT17thin film is of the best piezoelectric properties, which is attributed to a high degreeof alignment of ferroelectric domains in the MPB region and its largest grain size. TheNKBT17thin film exhibits the classical diffuse phase transition of a relaxor ferroelectric,which is discussed by compositional inhomogeneity and polar nanoregions（PNRs）.2. NKBT15-N100x （x=0,0.01,0.03,0.05,0.07） thin films were also prepared by MODmethod, and the phase structures, surface morphologies, residual stressses, erroelectricproperties, piezoelectric properties and leakage current of the NKBT15-N100x thin filmshave been sutdies. The NKBT15-3N thin film has the best crystallinity, the smallest elasticitymodulus （102.0Gpa）, hardness （5.1Gpa）, residual stress （297.0Mpa） and leakage current,and the largest remnant polarition and statistic d33eff（140pm/V）.