Phonons Damped by Proton Doping in Barium Zirconate

We show that protons strongly dampsome phonons in hydratedbariumzirconate. To show this, we performed terahertz spectroscopy and infraredreflection spectroscopy measurements on anhydrous and hydrous acceptor-dopedbarium zirconate sintered pellets. Last and Slater phonon modes arestrongly damped with proton doping, whereas phonons are not dampedwith trivalent dopants. This is due to picosecond motion of protons,such as hydroxyl rotation and attempt motion of proton hopping, coupledwith the phonon. This coupling strongly depends on the dopant, suggestingthat the proton motion is strongly influenced by the dopant. The resultsof Raman spectroscopy support this explanation. We consider that sucha dynamical long-range proton-lattice correlation will enablenew approaches to improve proton conduction in solid-state ionics.

Automated summary

We demonstrate that protons strongly inhibit certain phonons in hydrated barium zirconate. By conducting terahertz spectroscopy and infrared reflection spectroscopy measurements on anhydrous and hydrous acceptor-doped barium zirconate sintered pellets, we provide evidence for this effect. Last and Slater phonon modes are significantly suppressed with proton doping, while phonons are not damped with trivalent dopants. This phenomenon is attributed to the picosecond motion of protons, such as hydroxyl rotation and attempt motion of proton hopping, coupled with the phonon.