Abstract
We report results from visible and UV Raman spectroscopy studies of the phonon spectra of a polycrystalline sample of the prototypical perovskite type oxide BaZrO3 and a 500 nm thick film of its Y-doped, proton conducting, counterpart BaZr0.8Y0.2O2.9. Analysis of the Raman spectra measured using different excitation energies (between 3.44 eV and 5.17 eV) reveals the activation of strong resonance Raman effects involving all lattice vibrational modes. Specifically, two characteristic energies were identified for BaZrO3, one around 5 eV and one at higher energy, respectively, and one for BaZr0.8Y0.2O2.9, above 5 eV. Apart from the large difference in spectral intensity between the non-resonant and resonant conditions, the spectra are overall similar to each other, suggesting that the vibrational spectra of the perovskites are stable when investigated using an UV laser as excitation source. These results encourage further use of UV Raman spectroscopy as a novel approach for the study of lattice vibrational dynamics and local structure in proton conducting perovskites, and open up for, e.g., time-resolved experiments on thin films targeted at understanding the role of lattice vibrations in proton transport in these kinds of materials.
Highlights
Acceptor-doped perovskite type oxides, such as Y-doped BaZrO3 (BZO), are currently receiving considerable attention because of their proton conducting properties and concomitant potential as electrolytes for hydrogen fuel cells and gas separation membranes [1]
We report results from visible and UV Raman spectroscopy studies of the phonon spectra of a polycrystalline sample of the prototypical perovskite type oxide BaZrO3 and a 500 nm thick film of its Y-doped, proton conducting, counterpart BaZr0.8Y0.2O2.9
Apart from the large difference in spectral intensity between the non-resonant and resonant conditions, the spectra are overall similar to each other, suggesting that the vibrational spectra of the perovskites are stable when investigated using an UV laser as excitation source. These results encourage further use of UV Raman spectroscopy as a novel approach for the study of lattice vibrational dynamics and local structure in proton conducting perovskites, and open up for, e.g., time-resolved experiments on thin films targeted at understanding the role of lattice vibrations in proton transport in these kinds of materials
Summary
Acceptor-doped perovskite type oxides, such as Y-doped BaZrO3 (BZO), are currently receiving considerable attention because of their proton conducting properties and concomitant potential as electrolytes for hydrogen fuel cells and gas separation membranes [1]. The protons can diffuse through a repetition of proton transfers (jumps) from a specific oxygen atom to another one, and an intermediate reorientational motion of the O–H group between such transfers [2]. The ability of the protons to diffuse depends strongly on the vibrational dynamics of the system. The localized vibrational modes of protons, i.e. O–H stretching and O–H wagging (bending) modes, are known to affect the proton transfer and O–H reorientational motions [2, 3] and the dynamics of the oxygen atoms play an important role as they influence the proton jump distance [2, 4, 5]. Assisted proton transfer in oxides has been suggested both by theoretical analysis [6,7,8] and by time-resolved vibrational spectroscopy experiments [9, 10]
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