Ex-solution kinetics of nickel-ceria-doped strontium titanate perovskites

Abstract

Nickel ex-solution from La0.3Sr0.5NixTi1-xO3-delta (LSNxTA-) perovskites containing different nickel fractions (x = 0.04 and 0.16) is studied using temperature-programmed reduction (TPR) and chemisorption. Non-isothermal reduction of nickel occurs through two steps as confirmed using two-parameter Sestak-Berggren model, where the nuclei of nickel are formed at low temperatures, which grow through at elevated temperatures. The kinetic triplets (E-a, f(alpha), and ln A) are estimated from the Sestak-Berggren model. The nucleation at elevated temperature is the rate-determining step whose activation energy (E-a) is reduced with higher nickel loadings in the perovskite. Doping ceria at the A-site in LC0.04SN0.16TA- increases the dispersion of nickel, estimated using chemisorption studies in comparison to LSN0.16TA- perovskites. Physical characterization of sthe reduced perovskites using X-ray photo electron spectroscopy is used to correlate the ex-solution process with the Sestak-Berggren model.