Grain boundary segregation and high nonlinear I-V characteristics in Fe-added strontium titanate

Abstract

The nonlinear current-voltage (I-V) characteristics of SrTiO(3) have been improved greatly by inducing nonequilibrium segregation of Fe-acceptor dopant at grain boundaries. When Fe-doped SrTiO(3) samples with different Fe additions (0, 0.2, 0.5, 1, 2, and 3 mol%) were sintered at 1350 degrees C in H(2), metallic Fe particles were precipitated at grain boundaries and triple junctions. During subsequent air-annealing at 1100 degrees C, the metallic Fe in the H(2)-sintered samples oxidized as Fe(2)O(3) and FeO, and the Fe ions diffused along and segregated at the grain boundaries in the surface region of the sample. The annealed samples showed excellent nonlinear I-V characteristics (alpha approximate to 173), suggesting that an electrical potential barrier was formed at grain boundaries by the air-annealing. As the amount of Fe increased up to 2 mol%, the nonlinear properties considerably increased as long as the Fe ion diffusion into the bulk grains was not considerable. The present investigation shows the processing and applicability of Fe-doped SrTiO(3) as a new nonlinear device material.