Structural, dielectric and piezoelectric properties of (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3–Bi(Zn0.5Ti0.5)O3 thin films prepared by sol–gel method

Lead free (1−x)(0.8Bi0.5Na0.5Ti0.5O3–0.2Bi0.5K0.5TiO3)–xBiZn0.5Ti0.5O3 (x=0–0.06) (BNT–BKT–BZT) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by a sol–gel processing technique. The effects of BZT content on the structural, dielectric, ferroelectric and piezoelectric properties of the BNT–BKT–BZT thin films were investigated systematically. The BNT–BKT–BZT thin films undergo a transition from ferroelectric to relaxor phase with increasing temperature. The phase transition temperature decreases with the increase of BZT content. The BNT–BKT–BZT thin film with x=0.04 exhibits the best ferroelectric properties (Pmax=40 µC/cm2 and Pr=10 µC/cm2), largest dielectric constant (ε=560) and piezoelectric constant (d33=40 pm/V). This finding demonstrates that the BNT–BKT–BZT thin film has an excellent potential for demanding high piezoelectric properties in lead free films.