Catalytic Dynamics and Oxygen Diffusion in Doped PrBaCo2O(5.5+δ) Thin Films

Area of Science:

• Materials Science
• Solid State Chemistry
• Catalysis

Background:

• Double perovskites like PrBaCo2O5.5+δ (PrBCO) are promising for energy applications.
• Doping with Sr and Fe in Pr(Ba0.5Sr0.5)(Co1.5Fe0.5)O5.5+δ (PBSCFO) aims to enhance catalytic and sensing properties.
• Understanding oxygen diffusion and redox reactions is crucial for device performance.

Purpose of the Study:

• To epitaxially grow Sr and Fe codoped PrBCO thin films (PBSCFO).
• To investigate the electrical resistance behavior and oxidation processes under varying gas environments.
• To determine diffusion coefficients and activation energies for charge carriers.

Main Methods:

• Epitaxial thin film growth of PBSCFO.
• Electrical conductivity relaxation (ECR) measurements under switching reducing/oxidizing gases.
• Mathematical modeling using Fick's second law to analyze R(t) vs t data.
• Arrhenius analysis to determine activation energies (Ea).

Main Results:

• Two distinct oxidation processes involving cobalt ions (Co(2+)/Co(3+) and Co(3+)/Co(4+)) were identified.
• Diffusivity (D(T)) and relaxation time (τ(T)) for these processes were determined at various temperatures.
• Oscillatory behavior in dR(t)/dt plots suggests a layer-by-layer oxygen vacancy exchange mechanism.
• Activation energies for the identified diffusion processes were calculated.

Conclusions:

• PBSCFO thin films exhibit complex oxidation dynamics crucial for their function.
• The layer-by-layer diffusion mechanism provides insights into oxygen vacancy exchange.
• LnBCO thin films with similar doping strategies are excellent candidates for low/intermediate temperature energy conversion devices and gas sensors.