Main Content

Paper on "Potassium Diffusion in Mono- and Bi-Crystalline SrTiO3 - Mechanisms and Activation Energies" published Advanced Material Interfaces

J. Bernzen, C. Fuchs, T. Jacob, Q. Ma, T. Meyer, C. Jooss and K.-M. Weitzel

The diffusion of potassium in SrTiO3 (STO) single crystals is investigated as a
function of temperature. Charge attachment induced transport experiments
are employed inducing diffusion profiles in STO evolving with time.
Potassium concentration profiles, characterized ex-situ by ToF-SIMS depth
profiling, exhibited a bimodal shape indicating two different transport
pathways. Two diffusion coefficients are obtained for the two profiles. Their
temperature dependence is described using an Arrhenius approach, allowing
two activation energies to be derived from the data set. Utilizing DFT+U, the
ionic mobility of potassium along the crystal structure is simulated and
activation energies are determined for every trajectory. The transport pathway
with the larger diffusion coefficient is assigned to defect transport, most likely
via Sr vacancies. The transport pathway exhibiting the lower diffusion
coefficient is assigned to interstitial transport. In addition, the experiment is
repeated on a bicrystalline STO sample to investigate the effect of a grain
boundary on the ionic conductivity of the sample. As expected, the grain
boundary represents an additional diffusion path for the potassium ions. The
corresponding diffusion coefficient along the grain boundary is three orders of
magnitude larger than that for bulk diffusion. Atomically resolved structural
information in the grain boundary region is presented.

Three different transport pathways for K in SrTiO 3
have been identified in a single sample, i.e.
defect transport (1), interstitial transport (2) and
grain boundary transport (3)

Adv. Mater. Interfaces 2024, 2400338
Doi: https://doi.org/10.1002/admi.202400338