Piezoelectric enhancement and vacancy defect reduction of lead-free Bi0.5Na0.5TiO3-based thin films

To explore new lead-free piezoelectric materials that is both environmentally friendly and healthy to provide the possibility for material selection for microelectromechanical systems. Lead-free piezoelectric (1-x)(0.8Bi_0.5Na_0.5TiO₃-0.2Bi_0.5K_0.5TiO₃)-xBi(Ni_0.5Zr_0.5)O₃ thin films (abbreviated as BNT-BKT-xBNZ) (x=0.00, 0.01, 0.02, 0.03, 0.04) were prepared on Pt(111)/Ti/SiO₂/Si substrates by a sol-gel method. Impacts of Bi(Ni_0.5Zr_0.5)O₃ content on the microstructure, dielectric, ferroelectric, and piezoelectric properties were also investigated detailedly. It found that the Bi(Ni_0.5Zr_0.5)O₃ composition had a great influence on the increase of relaxor and the decrease of the oxygen vacancies, which is influential to the promotion of thin-film properties. Thin-film of BNT-BKT-0.02BNZ showed the optimum electrical properties with the polarization of 40.27 μC/cm², dielectric constants of 477 and effective inverse piezoelectric coefficient reach up to 125.9 p.m./V. Results revealed that the BNT-BKT thin films with 0.02 mol% Bi(Ni_0.5Zr_0.5)O₃-doped are a kind of lead-free piezoelectric materials with superior manifestations with a great development prospect for applications.