Abstract
The effect of nonstoichiometry (Sr/Ti ratio from 0.995 to 1.02) on the bulk and grain boundary contributions to the electrical response of strontium titanate (STO) ceramics is investigated. Nonstoichiometric STO exhibits lower electrical resistivity than its stoichiometric counterpart. This decrease is systematic for both Ti- and Sr-excess and with a greater effect on the grain boundary resistivity compared to bulk. Moreover, systematic variations with the degree of nonstoichiometry are observed for bulk and grain boundary conductivity, activation energy, and capacitance. These changes are correlated with a high concentration of point defects and induced by the nonstoichiometry, increasing the charge carrier concentration. As a result, nonstoichiometry can be used to tailor the microstructure and properties of strontium titanate, particularly grain boundary properties.
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