Effects of tantalum doping on microstructure and ferroelectric properties of Bi4Ti3O12 thin films prepared by a sol–gel method

Tantalum-substituted Bi4Ti3O12 (Bi4Ti3-x/5Tax/5O12, BTTO) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by sol–gel technology. The effects of various processing parameters, including Ta content (x=0∼0.08) and annealing temperature (500∼800 °C), on the growth and properties of thin films were investigated. X-ray diffraction analysis shows that the BTTO thin films have a bismuth-layered perovskite structure with preferred (117) orientation. With the increase of Ta content, the grain size of film decreased slightly, and highly (117)-oriented BTTO films were obtained in the composition of x=0.06. Ta doping on the B-site of Bi4Ti3O12 could induce the distortion of oxygen octahedral and decrease the oxygen vacancy concentration by a compensating effect. The highly (117)-oriented BTTO thin films with x=0.06 exhibits the maximum remanent polarization (2Pr) of 50 μC/cm2 and a low coercive field (2Ec) of 104 kV/cm, fatigue free characteristics up to ≧ 108 switching cycles.

► Tantalum-doped Bi4Ti3O12 thin films were prepared by sol–gel technology.
► Films show preferred (117) orientation.
► Tantalum-doping decrease the oxygen vacancy concentration.
► Tantalum-doping improved the ferroelectric and leakage current properties.