Effect of Sintering Atmosphere on Grain Boundary Segregation and Grain Growth in Niobium‐Doped SrTiO₃

Abstract

To investigate the donor segregation in grain boundary regions and its effect on grain growth in SrTiO3, SrTiO3 powder compacts were doped with Nb2O5 and sintered in air or in hydrogen. The Nb‐doped SrTiO3 sintered in air did not show any detectable Nb segregation at the grain boundary region while an appreciable segregation was observed in the space‐charge region of the sample sintered in H2. The observed donor segregation in H2 suggests a negative grain boundary charge and compensating positive space charge, which are the opposite to those in air. The negative grain boundary core was attributed to the segregation of inherently present acceptor impurities and the trapping of electrons at grain boundaries. In the H2‐sintered sample, where the added Nb ions were segregated in the space‐charge region, the grain growth was suppressed. This result may indicate that the grain growth suppression in H2 is due to the Nb solute drag of the boundary motion and the reduction in Ti vacancies.

Defect and electrical transport properties of Nb-doped SrTiO3

“…Similar lithium insertion experiments on perovskite structured materials, with Ti and Nb on the B-site, have suggested analogous results [38]. Xray photoelectron spectroscopy (XPS) on Nb-doped SrTiO 3 has also confirmed that the valance state of Nb is +V, even after sintering at 1360°C in highly reducing atmospheres (dry H 2 ) [39].…”

Correlation of microstructure and electrical conduction behaviour with defect structure of niobium doped barium stannate

“…It has been reported by Chung et al [24] that sintering atmosphere influences the grain growth behaviour of donor doped BaTiO 3 . A reducing atmosphere is conducive to grain growth due to increase in oxygen vacancies concentration.…”

Growth of single crystalline seeds into polycrystalline strontium titanate: Anisotropy of the mobility, intrinsic drag effects and kinetic shape of grain boundaries

“…The grain boundaries of strontium titanate are charged [56,57] and different intrinsic [21] or extrinsic [56][57][58] defects segregate or are depleted. The content of extrinsic defects ('solutes') is very low in the ceramic powder used in the current study [42].…”