Effect of niobium on electrical properties of Sr 0.8 Bi 2.3 (Ta 1-x Nb x ) 2 O 9+α thin films processed by sol–gel method

Abstract

Polycrystalline SBTN ferroelectric thin films were prepared by the sol–gel method with various Nb mole ratioson Pt/SiO₂/Si(100) substrates. The films were annealed at different temperatures and characterised in terms of phase and microstructure. A relatively well saturated hysteresis pattern was obtained at x=0.2 in Sr_0.8Bi_2.3(Ta_1-xNb_x)₂O_9+α thin films. At an applied voltage of 5 V, the dielectric constant ε _r and dissipation factor tan δ of a typical Sr_0.8Bi_2.3(Ta_1-xNb_x)₂O_9+α thin film (x=0.2) were about 236.2 and 0.034. Measured remanent polarisation 2P _r and coercive field E _c were 4.28 µC cm², and 38.88 kV cm¹ respectively. No fatigue was observed up to 6×10¹⁰ switching cycles at 5 V and the normalised polarisation reduced by a factor of only 4%.