Tunable Oxygen Diffusion and Electronic Conduction in SrTiO₃ by Dislocation‐Induced Space Charge Fields

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 SrTiO 3 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 °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 SrTiO 3 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.

High temperature creep‐mediated functionality in polycrystalline barium titanate

“…In ferroelectrics, theoretical work has suggested that dislocations can pin domain walls and, hence, should be able to influence dielectric losses for high‐power applications . The applicability of the 1‐dimensional doping concept, however, hinges on availability of single crystals, which can be deformed . Dislocations on a small scale can be introduced by indentation or surface treatments, but with these methods macroscopical changes in the ferroelectric properties cannot be reached.…”

“…7 This approach has demonstrated large changes in conductivity in plastically deformed TiO 2 and SrTiO 3 single crystals. [8][9][10] Similarly, dislocations have been proven to pin flux lines in superconductors 11 and to enhance the thermoelectric figure of merit by reducing thermal conductivity. 12 In ferroelectrics, theoretical work has suggested that dislocations can pin domain walls 13 and, hence, should be able to influence dielectric losses for highpower applications.…”

“…14 The applicability of the 1-dimensional doping concept, 8 however, hinges on availability of single crystals, which can be deformed. 9 Dislocations on a small scale can be introduced by indentation 15,16 or surface treatments, but with these methods macroscopical changes in the ferroelectric properties cannot be reached. While recent fundamental work by Ohsima et al 17 demonstrated that changes in illumination provide drastic changes in ductility of semiconductors, this may not be possible for ceramics in general.…”

Deformation-induced charge redistribution in ceria thin film at room temperature

“…It was previously reported that electrical conductivity can be modified by structural changes originating from the formation of dislocation [28,29,37,38], grain boundaries [10,21], surfaces [54], and interfaces [22][23][24]. The common observation in the modified electrical conductivity was the presence of oxygen vacancies.…”

Doping Strategies in Inorganic and Organic Materials

“…In TiO 2 (Figure 9) or SrTiO 3 the dislocations showed (apart from the sign) similar space charge effects. [33,34] As long as the spacing of the dislocation lines are pronounced, the overall conductivity effects are only perceptible if one measures along the onedimensional objects and as long as they are highly conducting. In all other cases the bulk effects dominate.…”