Enhanced crystal growth kinetics in cation-doped Sr_0.7Bi _2.3Ta₂O₉ ferroelectric thin films

Sr_0.7Bi_2.3Ta_1.7Ti_0.3O ₉ (SBTT) and Sr_0.7Bi_2.3Ta_1.7Zr _0.3O₉ (SBTZ) ferroelectric thin films were fabricated through partial substitution of Ta⁵⁺ ions in Sr_0.7Bi _2.3Ta₂O₉ (SBT) and crystal growth kinetics of ferroelectric Aurivillius phase was analyzed and compared for each thin film. Quantitative X-ray difraction (Q-XRD) analyses were performed on each thin film isothermally heated in the range of 730-760°C at 10°C intervals for different time periods. Activation energy and Avrami exponent values for Aurivillius crystal growth were determined by employing Johnson-Mehl-Avrami (JMA) isothermal kinetic analyses to the Q-XRD data. A reduction of ∼51 and ∼82 kJ/mol in activation energy was observed for the SBTT and SBTZ, respectively, which plays a major role in enhancing the crystal growth kinetics of SBTT and SBTZ thin films. A possible mechanism for the reduction in activation energy values was discussed based upon the ionic bond strength difference. The Avrami exponent values were determined as ∼1.0 for SBT, SBTT, and SBTZ thin films, indicating one-dimensional crystal growth with a diffusion-controlled mechanism at a decreasing nucleation rate.