Structural, optical, and electric properties of BNT–BT0.08 thin films processed by sol–gel technique

Thin films with the composition [(Bi0.5Na0.5)TiO3]0.92–[BaTiO3]0.08 (hereafter BNT–BT0.08) were deposited on Pt–Si by spin-coating from a stable sol precursor. The BNT–BT0.08 film, crystallized on the Bi0.5Na0.5TiO3 rhombohedral lattice, was obtained after annealing the film-gel at 700 °C. The films have a smooth surface (Rms = 2.76 nm) and grains with ferroelectric domains. The film showed a bandgap of 3.25 eV and a refractive index of 2.20 at a wavelength of 630 nm. The dielectric characteristics of BNT–BT0.08 thin films were measured at room temperature and 10 kHz the dielectric constant (e r) was 243 and the loss tangent (tanδ) was 0.38. The remnant polarization (P r) was 0.87 μC/cm2 and the coercive field (E c) was 220 kV/cm at 10 kHz and room temperature. The current density was approximately 2.7 × 10−5 A/cm2 at low electric fields (100 kV/cm). BNT–BT0.08 thin films shown piezoelectric properties (d 33eff = 100 pm/V) comparable to those of PZT thin films.