In-Situ Probing of Chemo-Mechanic Properties and Defects in Oxide-Based Ceramics Via Raman Spectroscopy
Authors: Rupp Jennifer L.M. 
Published: May 2020

The design of ceramic energy storage and conversion devices rely on the understanding of the components’ chemo-mechanic characteristics to describe their defect chemistry and volume changes with respect to stress, bias, pressure or temperature. Through this presentation we will focus on oxide-based ceramics and discuss opportunities to use ex- and in-situ Raman spectroscopy to explore lattice defect types and nature (such as intrinsic vs. extrinsic defects) in their characteristics. Often defects such as oxygen vacancies or dopant-oxygen vacancy associates (or lithium defects) are not directly accessable due to their light nature and require non-averaging spectroscopic approaches away from classic XRD to characterize the structures1-4. Also, electrochemical studies via impedance spectroscopy require additional modeling to shed light on the nature and presence of single and associate defects. Through this talk we discuss recent progress to probe lattice defect types on the examples of the binary oxide ceria and its solid solutions, and the perovskite SrTiO3-d, both of high use in energy applications. For ceria5, we explore the fascinating nature of near order characteristics via Raman spectroscopy and highlight findings towards EXAFS studies, and all that is missed by looking at XRD alone, for strained and doped structures ranging from bulk to thin films. On the example of Sr(Ti, Fe)O3-d, we demonstrate a new technique, being in operando Raman spectroscopy coupled with an electrochemical titration cell, to probe for smallest films how the chemical expansion can be tracked vs. oxygen nonstoichiomtry for various iron doping concentrations6.
Collectively, the insights on Raman spectroscopy describing the near order vibrations and their defect types and the opportunities for ex- and also in-situ probing with carrier pumps or vs. strain and dopants are discussed.

References:

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1. Sediva, T. Defferriere, N.H. Perry, H.L. Tuller, J.L.M. Rupp, In Situ Method Correlating Raman Vibrational Characteristics to Chemical Expansion via Oxygen Nonstoichiometry of Perovskite Thin Films. Advanced Materials, 1902493 (2019)