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Free keywords:
dislocations; electrical properties; mixed ionic electronic conductor; oxide ion diffusion; point defects
Abstract:
Plastic strain engineering was applied to induce controllable changes in electronic and oxygen ion conductivity in oxides by orders of magnitude, without changing their nominal composition. By using SrTiO3 as a model system of technological importance, and by combining electrical and chemical tracer diffusion experiments with computational modeling, it is revealed that dislocations alter the equilibrium concentration and distribution of electronic and ionic defects. The easier reducibility of the dislocation cores increases the n-type conductivity by 50 times at oxygen pressures below 10(-5) atm at 650 degrees C. At higher oxygen pressures the p-type conductivity decreases by 50 times and the oxygen diffusion coefficient reduces by three orders of magnitude. The strongly altered electrical and oxygen diffusion properties in SrTiO3 arise because of the existence of overlapping electrostatic fields around the positively charged dislocation cores. The findings and the approach are broadly important and have the potential for significantly impacting the functionalities of electrochemical and/or electronic applications such as thin film oxide electronics, memristive systems, sensors, micro-solid oxide fuel cells, and catalysts, whose functionalities rely on the concentration and distribution of charged point defects.
