Electrical characterization of the intergrowth ferrite Sr4Fe6O13+δ

Experimental data for thermopower, conductivity and oxygen content in Sr4Fe6O13+δ were obtained in the temperature range 750–1000°C and oxygen partial pressure between 10−17 and 0.5 atm. The results were utilized to obtain partial contributions of hole- and electron-like carriers in the total conductivity, to evaluate respective mobility parameters and to carry out model calculations of oxygen content in the oxide. The hole mobility is shown to be independent of temperature while mobility of electrons has temperature-activated character. The charge compensation of the electronic carriers occurs due to appearance of doubly charged oxygen interstitial ions and oxygen vacancies in the crystalline structure of the oxide. The conductivity evolves mainly over perovskite layers in the oxide at high pressure of oxygen while all structurally different positions of iron ions become available for electron-like carriers in the low-pressure limit. The oxygen ion contribution in total conductivity is shown to be essentially smaller than the contribution of electronic carriers.