Equilibrium Point Defect and Electronic Carrier Distributions near Interfaces in Acceptor‐Doped Strontium Titanate

Abstract

A mathematical model based on Frenkel's theory for charged defect segregation at interfaces is used to calculate the equilibrium grain boundary depletion layer widths and conductivity profiles in acceptor-doped SrTiO 3 ceramics. The calculations examine the effect of oxygen vacancy equilibration during annealing at moderate temperatures (ϳ1000 K) on the development of interfacial charge that influences grain boundary electrical properties at lower temperatures. Good agreement is demonstrated between the model predictions and experimental results reported in the literature.

Influence of Sr/Ti Stoichiometry on the Densification Behavior of Strontium Titanate

“…However, the influence of this mechanism, which is based on Ti termination depends on the solubility limit of Ti in SrTiO 3 . Additionally, both grain boundaries 10 and the surfaces 18,19 in the contact area are affected by space charge effects. Owing to the low defect formation energy of oxygen vacancies, the interface charge should be negative, 19 compensated by a positive space charge layer, e.g., a higher concentration of cation vacancies.…”

“…Additionally, both grain boundaries 10 and the surfaces 18,19 in the contact area are affected by space charge effects. Owing to the low defect formation energy of oxygen vacancies, the interface charge should be negative, 19 compensated by a positive space charge layer, e.g., a higher concentration of cation vacancies. It is possible that the diffusion in these regions is affected by changes in diffusivity due to the change in chemical potentials of the cation vacancies going from a Sr‐ to a Ti‐rich composition, within the solubility limits.…”

Synthesis and Characterization of Nanocrystalline SrTiO3

“…While electronic materials are widely investigated at nano-size, 1-3 this is not so much the case for ionically as well as mixed conducting materials, although they play a significant role in a variety of applications such as batteries, fuel cells, and sensors. [12][13][14][15][16][17][18][19][20] These grain-boundary cores have been found to be positively charged and hence to be accompanied by zones in which electron holes (h ) and oxygen vacancies (V O ) are depleted, the concentration of the latter ([V O ]) being depleted more strongly, because of the double charge leading to a quadratic effect compared with the hole depletion. 11 SrTiO 3 has attracted much attention due to both scientific and technological considerations.…”

Conductivity of iron‐doped strontium titanate in the quenched and degraded states

“…Defect reactions, mass‐action constants, and electron and hole mobilities are from Denk with the exception of the mobility from recent work by De Souza et al . A quenching formalism, instituted by many, was invoked to predict the defect populations when quenched to lower temperature, during which the ionic defects cannot re‐equilibrate. The simulated quenching formalism employed here of (a) equilibrating at high temperatures and then (b) freezing in the total population of ionic defects and allowing for only electronic charge redistribution, has been previously shown to be valid in acceptor‐doped BaTiO 3 systems …”