Short-range structure of proton conducting perovskite BaIn_{x}Zr_{1-x}O_{3-x/2} (x = 0-0.75)

TL;DR

This study uses infrared and Raman spectroscopy to analyze how doping levels and hydration affect the local structure of proton-conducting BaIn_xZr_{1-x}O_{3-x/2} perovskites, revealing that distortions enhance proton transport.

Contribution

It provides new insights into the relationship between local structural distortions and proton conductivity in doped perovskite oxides.

Findings

Doping causes significant local distortions in the structure.

Increased In concentration leads to more pronounced distortions.

Structural distortions correlate with improved proton conductivity.

Abstract

In a systematic study we investigate the effect of dopant level and hydration on the short-range structure of the proton conducting perovskite-type oxide BaIn_{x}Zr_{1-x}O_{3-x/2} (x = 0-0.75), using infrared and Raman spectroscopy. The results show that doping leads to significant local distortions of the average cubic structure of these materials. By increasing the In concentration from x = 0 to x = 0.75 new bands appear and grow in intensity in both the IR and Raman spectra, showing that the local distortions become successively more and more pronounced. The structural distortions are largely uncorrelated to the presence of oxygen vacancies, but instead are mainly driven by the size difference between the In^{3+} and Zr^{4+} ions, which leads to displacements of the cations and to tilting of the (In/Zr)O_{6} octahedra. Based on our results, we suggest that there is a threshold between x = 0.10 and x = 0.25 where the local structural distortions propagate throughout the whole perovskite structure. Comparison of our spectroscopic data with the proton conductivity reported for the same materials indicates that the presence of extended structural distortions are favorable for fast proton transport.