No abstract

H + -containing lanthanide-doped perovskites A (Ba, Sr etc.)B(Zr, Ce, Ti etc.)O 3 are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300-800°C). The comparison studies of the hydrated and non-hydrated Yb-doped BaZrO 3 and SrZrO 3 were performed by thermal expansion, medium-high temperature neutron and room-temperature high-pressure Raman scattering. Neutron diffraction and elastic/quasielastic studies carried out for BaZrO 3 ceramic show the presence of the protons, their successive diffusion above ∼600°C, and then their departure above 750°C (under vacuum). Phase transitions and their modification by proton insertion are discussed. A high-pressure Raman study of SrZrO 3 performed at room temperature in the diamond anvil cell reveals the presence of two pressure-induced phase transitions at about 5 and 22 GPa and confirms that proton insertion modifies the phase transition sequences.

We compare Raman and infrared spectra of the nuOH/OD modes in benzoic acid crystal powders at 7 K. The extremely sharp Raman bands contrast to the broad infrared profiles and suggest adiabatic separation of hydrogen (deuterium) dynamics from the crystal lattice. There is no evidence of any proton-proton coupling term. The assignment scheme is consistent with a quasisymmetric double-minimum potential, largely temperature independent. Tunnel splitting is a major band shaping mechanism, in addition to anharmonic coupling with lattice modes. The proton/deuteron dynamics are rationalized with nonlocal pseudoparticles and extended states. We propose a symmetry-related damping mechanism to account for the broad infrared profiles, as opposed to the sharp Raman bands. We assign spectral features to distinct interconversion mechanisms based on either pseudoparticle transfer or adiabatic pairwise transfer. We establish close contacts with theoretical models based on first-principles calculations.