Nonisothermal phase formation kinetics in sol-gel-derived strontium bismuth tantalate

Phase formation characteristics of Sr_0.7Bi_2.4Ta₂O₉ (SBT) powder, synthesized via the sol-gel and pyrolysis processes, was investigated using the thermal analysis technique. The two exotherms, appearing in the differential thermal analysis (DTA) curve, were identified as crystallization of fluorite phase and transformation of fluorite to Aurivillius phase, respectively, using x-ray diffraction. Nonisothermal kinetic analysis of the DTA results shows activation energy values for the formation of fluorite and Aurivillius phases as 192 and 375 kJ/mol, respectively, and Avrami exponent values for each reaction as 0.91 and 0.96, respectively. The results of this investigation are presented and discussed in detail to understand the phase formation mechanism in the SBT system.